Influenza-A infection in children

Management and control of communicable diseases in schools and other child care settings: systematic review on the incubation period and period of infectiousness

Background

Information on the incubation period and period of infectiousness or shedding of infectious pathogens is critical for management and control of communicable diseases in schools and other childcare settings.

Methods

We performed a systematic literature review (Pubmed and Embase) to identify and critically appraise all relevant published articles using incubation, infectiousness or shedding, and exclusion period as parameters for the search. No language, time, geographical or study design restrictions were applied.

Results

A total of 112 articles met the eligibility criteria. A relatively large number were retrieved for gastrointestinal diseases and influenza or respiratory syncytial virus, but there were few or no studies for other diseases. Although a considerable number of publications reported the incubation and shedding periods, there was less evidence concerning the period of infectiousness. On average, five days of exclusion is considered for measles, mumps, rubella, varicella and pertussis. For other diseases, such as most cases of meningococcal disease, hepatitis A and influenza exclusion is considered as long as severe symptoms persist. However, these results are based on a diverse range of study characteristics, including age, treatment, vaccination, underlying diseases, diagnostic tools, viral load, study design and definitions, making statistical analysis difficult.

Conclusions

Despite inconsistent definitions for key variables and the diversity of studies reviewed, published data provide sufficient quantitative estimates to inform decision making in schools and other childcare settings. The results can be used as a reference when deciding about the exclusion of a child with a communicable disease that both prevents exposure and avoids unnecessary absenteeism.

Clinical differences of influenza subspecies among hospitalized children

AIM

Clinical findings, mortality, and morbidity rates differ among influenza subspecies. Awareness of these differences will lead physicians to choose the proper diagnostic and therapeutic strategies and to foresee possible complications. The aim of this study was to evaluate the clinical differences of influenza subspecies among hospitalized children.

MATERIAL AND METHODS

Hospitalized children with proven influenza infection by polymerase chain reaction on nasopharyngeal swab specimens in our clinic, between December 2013 and March 2016, were enrolled. These children were divided into 3 groups as Influenza A/H1N1 (n=42), Influenza A/H3N2 (n=23), and Influenza B (n=35).

RESULTS

The median age of the children was 51.5 months (range, 3-204 months). The most common presenting symptoms were fever (n=83), cough (n=58), and difficulty in breathing (n=25). The most common non-respiratory findings were lymphadenopathy (n=18) and gastrointestinal system involvement (n=17). Sixty-two percent of the patients (n=62) had chronic diseases. H1N1 and H3N2 were significantly more common among patients with chronic neurologic disorders and renal failure, respectively. Leukopenia (n=32) and thrombocytopenia (n=22) were the most common pathologic laboratory findings. Neutropenia, elevated CRP levels, and antibiotic use were significantly more common among patients with H1N1 infection. Seven patients were transferred to the intensive care unit with diagnoses of acute respiratory distress syndrome (n=4), encephalitis (n=2), and bronchiolitis (n=1). Two patients with chronic diseases and H1N1 infection died secondary to acute respiratory distress syndrome.

CONCLUSIONS

Influenza A/H1N1 infection represented more severe clinical disease.

Clinical features of children hospitalized with influenza A and B infections during the 2012-2013 influenza season in Italy

Background

Influenza is a major public health issue worldwide. It is characterized by episodes of infection that involve hundreds of millions of people each year. Since that in the seasons 2010–2011 and 2011–2012 the circulation of FLUB was decreasing we evaluated the clinical presentation, demographic characteristics, admitting department, and length of stay in children who contracted influenza admitted to Bambino Gesù Children’s Hospital, during the 2012–2013 influenza season, with the aim to establish if the recover of FLUB was associated to a clinical worsening, in comparison with those due to FLUA.

Methods

A total of 133 respiratory specimens, collected from patients with symptoms of respiratory tract infections, positive for the Influenza A and B viruses (FLUA and B) were subtyped. Comparisons between the FLUA and FLUB groups were performed with the one-way ANOVA for continuous parametric variables, the Mann-Whitney test for non-parametric variables, or the Chi-Square test or Fisher’s exact test (if cells <5) for categorical variables.

Results

87.09 % of the FLUA isolates were the H1N1 subtype and 12.90 % were H3N2. Among the FLUB isolates, 91.54 % were the B/Yamagata/16/88 lineage and 8.45 % were the B/Victoria/02/87 lineage. The largest number of FLUA/H1N1 cases was observed in children less than 1 years old, while the B/Yamagata/16/88 lineage was most prevalent in children 3–6 years old. Fever was a common symptom for both FLUA and B affected patients. However, respiratory symptoms were more prevalent in patients affected by FLUA. The median length of stay in the hospital was 5 days for FLUA and 3 days for FLUB.

Conclusions

The clinical features correlated to different Influenza viruses, and relevant subtypes, were evaluated concluding that the increasing of FLUB in the season 2012–2013 was without any dramatic change in clinical manifestation. Our findings suggest, finally, that a stronger commitment to managing patients affected by FLUA is required, as the disease is more severe than FLUB.

Novel influenza A (H1N1): clinical features of pediatric hospitalizations in two successive waves

OBJECTIVE

To describe and compare the characteristics of children hospitalized with novel influenza A (H1N1) during two successive waves.

METHODS

This was a medical chart review of all children hospitalized in a French Canadian pediatric hospital in Montreal in the spring and fall of 2009 with a positive real-time polymerase chain reaction for novel influenza A (H1N1) and flu-like symptoms.

RESULTS

We included 202 children with a median age of 4.9 (range 0.1-18) years. Demographic and clinical features of the children in the two waves were similar. One or more underlying medical conditions were found in 59% of the children. Clinical findings at admission were: fever (98%), cough (88%), congestion/rhinorrhea (58%), gastrointestinal symptoms (47%), oxygen saturation below 95% (33%), sore throat (20%), and neurological symptoms (9%). Admission to the intensive care unit was required for 22 (11%) children, and 14 patients needed respiratory support. During the second wave, the median duration of stay was shorter (3 vs. 4 days, p=0.003) and oseltamivir was used more often (84% vs. 40%, p<0.001).

CONCLUSIONS

Children hospitalized during the two successive waves of H1N1 were mainly school-aged and suffered from moderate disease. Although clinical features and severity of disease were similar, oseltamivir was prescribed more frequently and the length of hospital stay was shorter in the second wave.

Hospital-acquired influenza: a synthesis using the Outbreak Reports and Intervention Studies of Nosocomial Infection (ORION) statement

Nosocomial influenza outbreaks occur in almost all types of hospital wards, and their consequences for patients and hospitals in terms of morbidity, mortality and costs are considerable. The source of infection is often unknown, since any patient, healthcare worker (HCW) or visitor is capable of transmitting it to susceptible persons within hospitals. Nosocomial influenza outbreak investigations should help to identify the source of infection, prevent additional cases, and increase our knowledge of disease control to face future outbreaks. However, such outbreaks are probably underdetected and underreported, making routes of transmission difficult to track and describe with precision. In addition, the absence of standardised information in the literature limits comparison between studies and better understanding of disease dynamics. In this study, reports of nosocomial influenza outbreaks are synthesised according to the ORION guidelines to highlight existing knowledge in relation to the detection of influenza cases, evidence of transmission between patients and HCWs and measures of disease incidence. Although a body of evidence has confirmed that influenza spreads within hospitals, we should improve clinical and virological confirmation and initiate active surveillance and quantitative studies to determine incidence rates in order to assess the risk to patients.

Control of an outbreak due to an adamantane-resistant strain of influenza A (H3N2) in a chronic care facility

BACKGROUND

Chronic care facility residents are at risk of severe influenza infection and death. Adamantanes have been used by chronic care facilities for influenza A prophylaxis; however, genotypic resistance has altered prophylaxis recommendations. An outbreak of influenza A (H3N2) in a chronic care facility housing neurologically impaired children and young adults and subsequent control measures are described.

PATIENTS AND METHODS

Resident charts were retrospectively reviewed. Isolates were characterized by strain identification and pyrosequencing.

RESULTS

Although 95 (97%) of 98 residents had been immunized against influenza at the start of the influenza season, 16 (84%) of 19 case patients were identified on the first floor. However, following implementation of enhanced infection control practices and adamantane prophylaxis, only 10 (13%) of 79 case patients were identified on the second floor. Subsequent pyrosequencing studies revealed a serine to asparagine mutation at position 31 of the M2 protein.

CONCLUSIONS

Enhanced infection control precautions and adamantane prophylaxis were used to control spread of influenza in a chronic care facility. This outbreak demonstrates the importance of timely and consistent implementation of infection control measures in controlling influenza outbreaks in long term care facilities and raises questions about a possible role for adamantanes in preventing transmission of adamantane-resistant influenza A viruses.

Febrile seizures associated with influenza A

To clarify the clinical impact of influenza A on the development of febrile seizures (FS), consecutive FS patients brought to our hospital between October 2003 and September 2004 were prospectively surveyed. Patients infected with influenza A (influenza A patients) and those uninfected with influenza (non-influenza patients) were compared with regard to clinical characteristics of FS. Influenza infection was determined by rapid antigen test and/or serologically. Associations of influenza A with atypical findings of FS, including partial seizures, prolonged seizures, multiple seizures during the same illness, and 30-min or longer prolonged postictal impairment of consciousness (PPIC), were analyzed by multiple logistic regression. A total of 215 patients (47 influenza A and 168 non-influenza patients) were enrolled in the study. Age was significantly higher in the influenza A group (39.85+/-22.16 months vs. 27.51+/-17.14 months, P<0.001). Of 42 patients aged 48 months or older, which corresponded to the 80th percentile for age, 15 (35.7%) were influenza A patients, with a significantly higher incidence of such patients than in the subgroup of patients aged 47 months or younger (32/173, 18.5%) (P=0.015). On multiple logistic regression analysis, influenza A was independently associated with PPIC (odds ratio: 4.44, 95% confidence interval: 1.52-12.95, P=0.006), but not with other atypical findings. The positive association of influenza A with PPIC suggests that influenza may affect state of consciousness at the same time that it induces seizures with fever.

Influenza A and febrile seizures in childhood

The aims of the present study are to identify predisposing factors of febrile seizures in influenza A infection and to clarify the special characteristics of febrile seizures in children with influenza A infection. Between January and July 2005, children hospitalized because of febrile seizures and subsequently confirmed influenza A infection were enrolled as subjects. Age-matched control subjects were those admitted as a result of influenza A infection but no febrile seizures (control 1) and children who developed febrile seizures with negative viral studies (control 2). Significant factors for the development of febrile seizures include: history of febrile seizures, family history of seizure disorders, and coexisting gastroenteritis. Independent risk factor for febrile seizures was history of febrile seizures (odds ratio 7.58, 95% confidence interval CI 1.48 to 38.84, P = 0.015). When compared with children who developed febrile seizures with negative virus studies, children who developed febrile seizures in influenza A infection had a significantly higher maximum body temperature, shorter duration of fever before seizure onset, and more frequent occurrence of partial seizures. Current episode represented first seizure in 26.5% of children infected with influenza A as compared with 50% of children whose virus studies were negative (P = 0.04). The findings suggest that effective vaccination may prevent development of febrile seizures, especially in those patients with past history of febrile seizures. Rapid diagnostic testing for influenza infection in the management of complex febrile seizures, especially during influenza season, is cost-effective.

Respiratory viral infections drive chemokine expression and exacerbate the asthmatic response

A number of investigations have linked respiratory vial infections and the intensity and subsequent exacerbation of asthma through host response mechanisms. For example, it is likely that the immune-inflammatory response to respiratory syncytial virus can cause a predisposition toward an intense inflammatory reaction associated with asthma, and adenovirus might cause exacerbation of the immune response associated with chronic obstructive pulmonary disease. In each of these situations, the host's immune response plays a critical mechanistic role through the production of certain cytokines and chemokines. Specific aspects of these augmented immune responses are determined by the biology of the virus, the genetic variability of the host, and the cytokine-chemokine phenotype of the involved tissue. For instance, the type 1/type 2 cytokine ratio in the airways during infection with rhinovirus determines how long the viral infection endures. By this same theory, it has been demonstrated that chemokine levels produced during respiratory syncytial virus infection determine host responses to later immune stimuli in the lung, with the potential to augment the asthmatic response. Further research in this area will clarify cytokines, chemokines, or cell targets, which will provide the basis for next-generation therapies.

Role of viral infections in the etiology of febrile seizures

The role of viral infection in the etiology of febrile seizures is a relatively neglected field of neurologic research. A National Institutes of Health Consensus Conference (1981) omitted reference to causes of infections and the role of fever in febrile seizures, and emphasized outcome and anticonvulsant treatment. In an earlier review of the world literature (1924-1964), except for roseola infantum, viral infections as a cause of febrile seizures were rarely diagnosed. The present review includes reports of viruses most commonly associated with febrile seizures in the last decade, especially human herpesvirus-6 and influenza. The specificity and neurotropic properties of some viruses in the febrile seizure mechanism, a possible encephalitic or encephalopathic pathology, and the essential role of fever and height of the body temperature as a measure of the febrile seizure threshold are discussed. Cytokine and immune response to infection, and a genetic susceptibility to febrile seizures are additional etiologic factors. Future research should emphasize early detection of causative viruses, the nature of viral neurotropism, and the role of cytokines in fever induction. Trials of antiviral agents and vaccines, with attention to safety concerns, and more effective antipyretics would address the febrile seizure mechanism more specifically than anticonvulsant therapies.

C-reactive protein and leukocytes do not reliably indicate severity of influenza a infection in childhood

Influenza in children may mimic other infections leading to insufficient treatment. Determination of parameters that facilitate diagnosis and indicate severity would be useful to optimize treatment modalities. We prospectively screened 432 children for influenza infection. Forty-six children at the age of 4 weeks to 14 years (median, 18 months) with confirmed influenza A infection were analyzed. A clinical score of illness severity was calculated from the symptoms presented. To evaluate the dependency of the clinical score on C-reactive protein value, leukocyte count, age, and days of hospitalization, correlation and regression analyses were carried out. Neither the C-reactive protein values (median, 0.85 mg/dL; range, 0.2-18.6; r=0.14; p=0.35) nor the leukocyte counts (median, 7.95 G/L; range, 3.5-17.6; r=-0.14, p=0.34) correlated significantly with the clinical score of influenza severity. Thus, in daily clinical practice, C-reactive protein and leukocytes seem to be insufficient parameters to describe the clinical severity of influenza A infection in children.

Rates of hospitalisation for influenza, respiratory syncytial virus and human metapneumovirus among infants and young children

To inform the development of a national influenza immunisation programme and the potential role of antiviral drugs in young children, we studied 613 children aged 71 months or younger who attended Leicester Childrens' Hospital during winter 2001-2002. During periods of respiratory syncytial virus (RSV), influenza, and human metapneumovirus activity, an estimated 12.2% (95% CI: 11.4-13.1), 7.1% (6.3-7.9), and 2.5% (2.1-2.9), respectively, of all medical cases assessed in the hospital were associated with these infections. The respective rates of hospital assessments for RSV, influenza, and human metapneumovirus (HMPV) were 1042 (95% CI: 967-1021), 394 (348-443), and 223 (189-262) per 100,000 children, and for admissions were 517 (465-574), 144 (117-175), and 126 (101-156) per 100,000. Few children with influenza had a prior risk factor. Children with influenza were admitted a median of 4 days after onset of illness and none was coded at discharge as influenza. We conclude that antivirals have little role in the hospital management of children with influenza. Our data provide health economists with information to evaluate the place of universal immunisation of young children against influenza. Hospitalisation rates decreased markedly with referral age, so vaccine would need to be given in early infancy for maximum benefit.

Influenza-associated deaths among children in the United States, 2003-2004

BACKGROUND

Although influenza is common among children, pediatric mortality related to laboratory-confirmed influenza has not been assessed nationally.

METHODS

During the 2003-2004 influenza season, we requested that state health departments report any death associated with laboratory-confirmed influenza in a U.S. resident younger than 18 years of age. Case reports, medical records, and autopsy reports were reviewed, and available influenza-virus isolates were analyzed at the Centers for Disease Control and Prevention.

RESULTS

One hundred fifty-three influenza-associated deaths among children were reported by 40 state health departments. The median age of the children was three years, and 96 of them (63 percent) were younger than five years old. Forty-seven of the children (31 percent) died outside a hospital setting, and 45 (29 percent) died within three days after the onset of illness. Bacterial coinfections were identified in 24 of the 102 children tested (24 percent). Thirty-three percent of the children had an underlying condition recognized to increase the risk of influenza-related complications, and 20 percent had other chronic conditions; 47 percent had previously been healthy. Chronic neurologic or neuromuscular conditions were present in one third. The mortality rate was highest among children younger than six months of age (0.88 per 100,000 children; 95 percent confidence interval, 0.52 to 1.39 per 100,000).

CONCLUSIONS

A substantial number of influenza-associated deaths occurred among U.S. children during the 2003-2004 influenza season. High priority should be given to improvements in influenza-vaccine coverage and improvements in the diagnosis and treatment of influenza to reduce childhood mortality from influenza.

Serious and lethal respiratory tract infections of viral etiology in children

Viruses may lead to serious and lethal pulmonary infections in immunocompetent and immunocompromised children. Series of children with acute respiratory distress syndrome and series of children requiring extracorporeal membrane oxygenation, as well as reported series of nosocomial viral illness, offer an insight into the extent of serious viral disease documented in the medical literature. Series of children with specific viral respiratory illness also will be reviewed, as will the means of diagnosis in these groups of patients. Copyright © 2000 by W.B. Saunders Company

Management of influenza virus infections with neuraminidase inhibitors: detection, incidence, and implications of drug resistance

Although influenza vaccination remains the primary method for the prevention of influenza, efficacy may be limited by a poor match between the vaccine and circulating strains and the poor response of elderly patients. Hence, there is an important role for antiviral therapy in the management of influenza. While amantadine and rimantadine have been available for the treatment of influenza in some countries for several years, they are only effective against influenza A viruses, they can have neurological and gastrointestinal adverse effects, and resistant virus is rapidly generated. Neuraminidase inhibitors, a new class of drug, are potent and specific inhibitors of all strains of influenza virus, and they have minimal adverse effects. The greatest benefit is seen in those patients presenting <30 hours after development of influenza symptoms, those with severe symptoms or those in high-risk groups. In addition to treatment of the infection, both drugs are effective prophylactically and have been shown to limit spread of infection in close communities, such as families and in nursing homes. No resistant virus strains have been isolated from normal individuals treated with zanamivir. Resistant virus can be isolated from approximately 1% of adults and 5% of paediatric patients with influenza treated with oseltamivir. However, infectivity of mutant viruses is generally compromised. Governments spend millions of dollars on influenza vaccination campaigns; however, once influenza virus is circulating in the community, vaccination cannot limit the spread of disease. A greater promotion of the use of neuraminidase inhibitors for the treatment and prevention of influenza could have a significant impact on limiting its spread. This could result in saving millions of dollars, not only in direct costs associated with medical and hospital care, but also significant savings in indirect costs associated with the loss of productivity at work, school and home environments. For the benefit of all communities, there needs to be a greater awareness of the symptoms of influenza and the efficacy of neuraminidase inhibitors in disease treatment.

Recurrence of febrile seizures in the respiratory season is associated with influenza A

OBJECTIVES

To investigate the association of viral infections and febrile seizures (FS).

STUDY DESIGN

From April 1998 to April 2002, a prospective, population-based study was carried out among general practitioners to assess the incidence of FS in their practices. Data thus obtained were compared with the incidence of common viral infections recorded in a national registry. Poisson regression analysis was performed to investigate whether the season or the type of infection was associated with the variation observed in FS incidence.

RESULTS

Throughout the 4-year period, 267 of 303 (88%) of general practitioners in the Dutch province of Friesland participated in the study. The estimated observation period was approximately 160,000 patient-years. We registered 654 cases of FS in 429 children. The estimated incidence of FS was 2.4 in 1000 patient-years. Poisson regression analysis revealed a positive correlation between recurrent FS and influenza A ( P = .01).

CONCLUSIONS

Our study suggests a relation between recurrent FS and influenza A. Influenza vaccination should be considered in all children with a history of FS.

Influenza virus and CNS manifestations

Neurological involvement during influenza infection has been described during epidemics and is often consistent with serious sequelae or death. An increasing incidence of influenza-associated encephalitis/encephalopathy has been reported in Japan, mainly in children. A variety of other clinical CNS manifestations, such as Reye's syndrome, acute necrotising encephalopathy (ANE), and myelitis as well as autoimmune conditions, such as Guillain-Barre's syndrome, may occur during the course of influenza infection. Virological diagnosis is essential and based on virus isolation, antigen detection, RNA detection by PCR, and serological analyses. Neuroimaging with CT and MRI of the brain are of prognostic value. The pathogenic mechanisms behind the influenza CNS complications are unknown. The treatment is symptomatic, with control of vital functions in the intensive care unit, antiepileptic medication and treatment against brain oedema.

Nosocomial influenza in children

Influenza is the most important cause of acute respiratory illness leading to hospitalization among children during community epidemics. This illness can cause extensive nosocomial outbreaks with serious morbidity and mortality among specific groups of children. Paediatric patients with community-acquired influenza and healthcare workers are the main reservoir for the nosocomial spread of the virus. During epidemics in the community, testing for influenza should be requested in all children with compatible symptoms admitted in the hospital, and measures should be introduced for the prevention or early control of an outbreak. Recent advances in the management of influenza include rapid diagnoses based on antigen detection and the identification of the new neuraminidase inhibitors zanamivir and oseltamivir. Annual vaccination against influenza of children with high-risk conditions, their family members and healthcare workers is the principle measure for the prevention of nosocomial outbreaks. Although vaccination against influenza appears to be cost-effective at all ages in terms of prevention of illness, related hospitalizations, deaths, reduction of healthcare costs and productivity loss, vaccination coverage among target groups is limited.

Influenza diagnosis and treatment in children: a review of studies on clinically useful tests and antiviral treatment for influenza

BACKGROUND

Prompt testing for influenza can help guide clinical management of patients with suspected influenza. Three antiviral medications, amantadine, oseltamivir and zanamivir, are approved for treatment of influenza in children. Rimantadine and ribavirin have also been used.

OBJECTIVES

To review the published evidence on clinically useful diagnostic tests and antiviral treatment for influenza virus infections in children.

METHODS

Studies published from 1966 through September 2002 were reviewed on clinical diagnosis, immunofluorescence and rapid influenza tests and on antiviral treatment of influenza virus infections among pediatric populations.

RESULTS

No studies assessed the accuracy of clinical diagnosis of influenza in children compared with viral culture. Compared with viral culture, direct immunofluorescence antibody and indirect immunofluorescence antibody tests for influenza had fair to moderate median sensitivities and high median specificities, whereas rapid influenza diagnostic tests had moderate median sensitivities and moderately high median specificities. No randomized, placebo-controlled studies were found of amantadine or rimantadine for treatment of influenza A. In a few separate controlled studies, oseltamivir, zanamivir and ribavirin each reduced symptom duration of influenza compared with placebo.

CONCLUSIONS

Additional data are needed about the accuracy of clinical diagnosis of influenza in children. Although direct immunofluorescence antibody staining, indirect immunofluorescence antibody staining and rapid tests are moderately to reasonably accurate in detecting influenza virus infections in children, physicians should use clinical judgment and local surveillance data about circulating influenza viruses when interpreting test results. Further controlled studies of the efficacy, adverse effects and emergence of antiviral resistance during treatment of influenza are needed for all of the antiviral drugs.

Nosocomial influenza at a Canadian pediatric hospital from 1995 to 1999: opportunities for prevention

Nineteen cases of nosocomial influenza occurred at a pediatric hospital during a 5-year period. Only one of the nine children with chronic health conditions had been immunized. Length of stay was prolonged for seven children, with three intensive care unit admissions. We have now implemented strategies to decrease nosocomial influenza infection.

Outbreaks of influenza A virus infection in neonatal intensive care units

BACKGROUND

Outbreaks of nosocomial influenza virus infections have been described rarely during childhood and even less so in the neonatal period.

METHODS

We report 30 neonates admitted to 2 neonatal intensive care units with nosocomial influenza A virus infection, which occurred in 2 outbreaks during 1999. Risk factors for infection were evaluated, and control measures were adopted. Virus was detected by indirect immunofluorescence antibody screen. Any infant with nasopharyngeal aspirate positive for influenza A virus was considered infected.

RESULTS

Of 95 infants screened 30 were positive for influenza A virus (31.5%). Mean birth weight was 1622 g, and mean gestational age was 31 weeks in the infected group. In the noninfected group mean birth weight was 2594 g and mean gestational age was 36.4 weeks. Low birth weight, short gestational age, twin pregnancy and mechanical ventilation were identified as risk factors for infection. Clinical symptoms were seen in 22, and 8 were asymptomatic. Clinical features were predominantly respiratory and digestive. The outcome was favorable in all cases.

CONCLUSIONS

Infection by influenza virus has to be considered as a possible cause of nosocomial infection in the neonatal period. Control measures and prevention are important.

Tumor necrosis factor alpha exerts powerful anti-influenza virus effects in lung epithelial cells

Previous studies have associated influenza virus-induced expression of inflammatory cytokines, including tumor necrosis factor alpha (TNF-alpha), with influenza pathogenesis in the human respiratory tract and have suggested that alpha and beta interferons are the first cytokines recruited to counteract such infection. However, we report here that TNF-alpha has powerful anti-influenza virus activity. When infected with influenza virus, cultured porcine lung epithelial cells expressed TNF-alpha in a dose-dependent manner. Expression of TNF-alpha was induced only by replicating virus. TNF-alpha showed strong antiviral activity against avian, swine, and human influenza viruses, and the antiviral effect of TNF-alpha was greater than that of gamma or alpha interferon. These findings suggest that TNF-alpha serves as the first line of defense against influenza virus infection in the natural host.

Clinical courses of croup caused by influenza and parainfluenza viruses

Influenza viruses have occasionally been associated with severe manifestations of croup, but no comparative studies of different viral etiologies are available. In a retrospective study we compared the clinical courses of croup caused by influenza and parainfluenza viruses in hospitalized children. By several indicators the clinical picture of croup caused by influenza viruses was significantly more severe than that caused by parainfluenza viruses.

Influenza A infection is an important cause of febrile seizures

OBJECTIVES

To compare the incidence of febrile seizures in children hospitalized for influenza A infection with parainfluenza and adenovirus infection and to examine the hypothesis that children hospitalized for influenza A (variant Sydney/H3N2) during the 1998 season in Hong Kong had more frequent and refractory seizures when compared with other respiratory viruses, including the A/Wuhan H3N2 variant that was present in the previous year.

METHODS

Medical records of children between 6 months and 5 years of age admitted for influenza A infection in 1998 were reviewed. For comparison, records of children of the same age group with influenza A infection in 1997, and with parainfluenza and adenovirus infections between 1996 and 1998 were reviewed. Children who were afebrile or who had an underlying neurologic disorder were excluded.

RESULTS

Of children hospitalized for influenza A in 1998 and 1997, 54/272 (19.9%) and 27/144 (18.8%) had febrile seizures, respectively. The overall incidence of febrile seizures associated with influenza A (19.5%) was higher than that in children hospitalized for parainfluenza (18/148; 12.2%) and adenovirus (18/199; 9%) infection, respectively. In children who had febrile seizures, repeated seizures were more commonly associated with influenza A infection than with parainfluenza or adenovirus infection (23/81 [28%] vs 3/36 [8.3%], odds ratio [OR] 4.3, 95% confidence interval: 1.2 to 15.4). Alternatively, children with influenza A infection had a higher incidence (23/416, 5.5%) of multiple seizures during the same illness than those with adenovirus or parainfluenza infection (3/347, 0.86%; OR 6.7, 95% confidence interval: 2.0-22.5.) The increased incidence of febrile seizures associated with influenza A was not attributable to differences in age, gender, or family history of febrile seizure. Multivariate analysis, adjusted for peak temperature and duration of fever, showed that hospitalized children infected with infection A had a higher risk of febrile seizures than those who were infected with parainfluenza or adenovirus (OR 1.97). Influenza A infection was a significant cause of febrile seizure admissions. Of 250 and 249 children admitted to Queen Mary Hospital for febrile seizures in 1997 and 1998, respectively, influenza A infection accounted for 27 (10.8%) admissions in 1997 and 54 (21.7%) in 1998. During months of peak influenza activity, it accounted for up to 35% to 44% of febrile seizure admissions. In contrast, parainfluenza, adenovirus, respiratory syncytial virus, and influenza B had a smaller contribution to hospitalizations for febrile seizures, together accounting for only 25/250 (10%) admissions in 1997 and 16/249 (6.4%) in 1998.

CONCLUSION

The influenza A Sydney variant (H3N2) was not associated with an increased risk of febrile seizures when compared with the previous influenza A Wuhan variant (H3N2) or H1N1 viruses. However, in hospitalized children, influenza A is associated with a higher incidence of febrile seizures and of repeated seizures in the same febrile episode than are adenovirus or parainfluenza infections. The pathogenesis of these observations warrants additional studies. Complex febrile seizures, particularly multiple febrile seizures at the time of presentation, have been thought to carry an adverse long-term prognosis because of its association with a higher incidence of epilepsy. Repeated febrile seizures alone, particularly if associated with influenza A infection, may not be as worrisome as children with complex febrile seizures because of other causes, which requires additional investigation. This may subsequently have an impact on reducing the burden of evaluation in a subset of children with complex febrile seizures.

Cost-effectiveness of influenza vaccination in high-risk children in Argentina

OBJECTIVES

our study aimed to evaluate the cost-effectiveness of influenza vaccination in high-risk children in Argentina.

METHODS

a decision analysis model was performed, using data from published and unpublished sources, to compare two strategies--to vaccinate or not to vaccinate. We simulated the expected consequences of vaccination on direct medical costs, related to disease management and indirect costs, related to lost parental working days (absenteeism).

RESULTS

Using base-case assumptions vaccination of high-risk children aged 6 months to 15 years old, in Argentina (estimated cohort of 1184748) would prevent 207331 cases of influenza, resulting in a reduction of 58052 days of hospitalization and 207331 outpatient visits. Vaccination would lead to net savings of US$ 11894870 per vaccinated cohort (US$ 10.04 per vaccinated child).

CONCLUSION

our economic analysis shows that in Argentina, routine vaccination of high-risk children against influenza would be cost saving for society.

Critical influenza virus infection

OBJECTIVE

To determine the risk of death from influenza infection in children with chronic underlying disease.

METHODOLOGY

An 18-year retrospective study of children with 'critical' influenza A or B virus infection, defined as requiring admission to intensive care or resulting in death, but excluding laryngotracheobronchitis (LTB). Influenza infection was diagnosed by viral culture and/or immunofluorescence of respiratory secretions. Patients with LTB were analysed separately.

RESULTS

There were 27 cases of critical influenza virus infection over the study period, comprising 26 admissions to the intensive care unit (excluding LTB) and one death on the general wards. Thirteen (48%) of the 27 children had chronic underlying disease. In addition, 12 children with LTB were admitted to the intensive care unit. The LTB children were older and less likely to have chronic underlying disease. Nosocomial infection caused seven (26%) of the 27 critical infections. Nine (33%) of the 27 children with critical influenza died. Six (46%) of 13 children with chronic underlying disease and influenza admitted to intensive care died, compared with three of 14 (21%) without any underlying disease (odds ratio = 3.1, 95% confidence interval 0.6-14.0).

CONCLUSIONS

Critical life-threatening influenza virus infection was uncommon, but the mortality was high (33%), particularly in children with chronic underlying disease. Nosocomial infection with influenza was an important cause of admission to intensive care.

Comparison of influenza A and influenza B virus infection in hospitalized children

BACKGROUND

Influenza A and B viruses were cocirculating in Australia in the winter of 1997.

OBJECTIVE

To compare the clinical and demographic features of children with influenza A or influenza B virus infection admitted to a paediatric tertiary referral centre.

METHODOLOGY

Retrospective chart review of 91 hospitalized children with culture-proven influenza A or B virus infection during 1997.

RESULTS

Thirty-six (56%) of 64 children with influenza A were under 12 months of age compared with seven (26%) of 27 children with influenza B virus infection (P = 0.02). Influenza B virus infection was more common in children with underlying medical problems (P = 0. 01). Neurological manifestations were present in eight (12.5%) of 64 children with influenza A and none with influenza B virus infection (P = 0.09). There were no significant differences in signs and symptoms of children with influenza A and B virus infection, in severity of illness or in duration of hospital stay.

CONCLUSIONS

A greater proportion of children admitted with influenza A virus infection were under 12 months of age. Influenza B virus infection is associated more commonly with underlying medical disorders. It is not possible to differentiate between influenza A or B virus infection from presenting clinical signs and symptoms.

Influenza

Influenza is an acute respiratory illness of global importance that causes considerable morbidity and mortality every year. At the beginning of the millennium, influenza will still be an emergent or re-emergent infection because of the viral ability to mutate. Global influenza surveillance indicates that influenza viruses may vary within a country and between countries and continents during an influenza season. Virologic surveillance is of critical importance in monitoring antigenic shift and drift. Disease surveillance is important in assessing the impact of the epidemics. Both types of information provide the basis of vaccine composition and the correct use of antivirals. Laboratory diagnosis is of critical importance for the global surveillance of influenza and may allow the timely use of antiviral drugs. Viral isolation remains the gold standard for laboratory diagnosis; however, several new rapid diagnostic tests are available or in development. The clinical spectrum of the disease varies from asymptomatic infection to the classic flu syndrome, and respiratory and nonrespiratory complications are observed particularly in high-risk groups. Current inactivated influenza vaccines have shown efficacy and effectiveness in preventing influenzalike illness, hospitalization for pneumonia, and death and in reducing health care costs. Because of the annual administration of the vaccine and the short period of time where it can be administered, strategies directed at improving vaccine coverage are of critical importance. In this sense, experiences obtained in different countries, such as with the National Immunization Campaigns developed in Argentina, provide one model of massive vaccine administration. In addition to current vaccines, new live attenuated vaccines will permit a most effective prevention of influenza in the community in the near future. A new type of antiviral, neuraminidase inhibitors, offers valuable benefits in the prevention and treatment of influenza A and B. A future pandemic of influenza seems inevitable. There is wide recognition that preparation for the next pandemic requires that infrastructure be in place during interpandemic periods for implementing preventive and therapeutic measures. The WHO has established a pandemic influenza task force, and a number of countries in Latin America have developed formal pandemic plans. These national and international efforts are essential to reduce the mortality and morbidity in the next influenza pandemic.

Influenza A virus outbreak in a neonatal intensive care unit

BACKGROUND

Nosocomial infections with influenza virus are rarely recognized in neonatal intensive care units (NICU). An outbreak of influenza A virus infection in the NICU of an urban county hospital during the 1997 to 1998 influenza season is reported.

METHODS

Clinical and virologic data were recorded in all symptomatic NICU patients after influenza A infection was diagnosed in one infant in October, 1997.

RESULTS

Influenza A/H3N2 was isolated from two of four symptomatic infants. The application of rapid diagnostic techniques for the characterization of influenza virus infection allowed the timely institution of basic infection control measures, limiting this outbreak. Resistance to amantadine was documented for the first time in this patient population by reverse transcription-PCR within 48 h of treatment in one case.

CONCLUSIONS

Prevention by immunization is a priority in those caring for high risk NICU patients.

Influenza control in acute care hospitals

BACKGROUND

Influenza causes increased morbidity and mortality among patients in longterm care facilities, but little information is available on the impact of influenza in acute care settings. We wished to have such information when revising our hospital influenza control policy.

METHODS

We reviewed recent reports of influenza among patients in acute care hospitals and surveyed large (approximately 500-bed) acute care teaching hospitals by telephone to determine the nature of their influenza control policies.

RESULTS

Seventeen reports of influenza outbreaks in acute care hospitals were published from 1959 to 1994. Influenza A caused 13 of these outbreaks. Five involved children and 12 involved adults. The mean number of patients in each outbreak was 14 (range 1 to 49), with a mortality rate of 0% to 50% (median 0%, mean 6.5%). Health care workers were implicated in transmission in five reports. Vaccine was used infrequently during the outbreaks, and use of chemoprophylaxis was not reported. Our survey of current practices in 15 university-affiliated hospitals from 12 states revealed that all offered vaccine in the fall but none required either immunoprophylaxis or chemoprophylaxis at any time. Only three had formal policies detailing management of influenza in the hospital.

CONCLUSIONS

Nosocomial influenza in acute care hospitals is infrequently reported and associated with a low mortality rate. Health care workers rarely comply with preventive measures, and few institutions have formal influenza control policies.

Seasonal onset of initial colonisation and chronic infection with Pseudomonas aeruginosa in patients with cystic fibrosis in Denmark

BACKGROUND AND METHODS

To assess the relation between seasonal variation and the onset of initial and chronic Pseudomonas aeruginosa infection, 300 Danish patients with cystic fibrosis were investigated. A retrospective analysis based on case reports was performed to identify the date and year of initial and chronic P aeruginosa infection from 1965 to 1990.

RESULTS

Sixty six per cent of the patients contracted their initial P aeruginosa colonisation and 68% contracted chronic infection during the winter months (October to March). Despite major changes in treatment, including improved and intensified antibiotic treatment, during the investigation period in our cystic fibrosis centre, the seasonal difference in P aeruginosa infection persisted.

CONCLUSIONS

As respiratory virus infections have the same seasonal distribution in Denmark such infections may pave the way for P aeruginosa and thus explain the parallel seasonal occurrence of this pathogen in patients with cystic fibrosis.

Viral infections and recurrences of febrile convulsions

To determine whether complicated febrile seizures occur more often in children with a proven viral infection, we performed viral examinations on 144 children with febrile convulsions, of whom 112 had simple and 32 had complicated seizures. A diagnosis of virus infection was verified in 46% of the former patients and 53% of the latter. Three adenoviruses, one parainfluenza virus type 2 and one type 3, one respiratory syncytial virus, one echovirus type 11, one herpes simplex virus type 2, and one influenza B virus were isolated from the cerebrospinal fluid. A simple febrile convulsion occurred in seven children with a positive cerebrospinal fluid viral isolation, and two had a complex febrile seizure. In a follow-up of 2 to 4 years (mean 3.3 years), 21 of the 107 children with simple seizures (19.6%) and 3 of the 32 children with complicated seizures (9.4%) had recurrent febrile seizures. The children with positive evidence for a viral infection, even with a virus isolated from the cerebrospinal fluid, had no more recurrences than those without any proven viral infection. We conclude that children with a proven viral infection have no worse prognosis than those without.

Influenza in children with cancer

We prospectively followed a group of unimmunized, immunosuppressed children with cancer to determine their relative risk of influenza and the severity of infection compared with those of siblings or matched community controls. The incidence of influenza infection was higher in children with cancer (23/73, 32%) than in control subjects (10/70, 14%, p = 0.02). A preseason hemagglutination inhibition titer greater than or equal to 1:32, generally used as a marker of successful immunization in vaccine trials, was protective for all children in the control groups, but did not prevent influenza infection in 24% of the patients with cancer. Infection rates of patients and community controls with titers greater than or equal to 1:32 differed significantly (p = 0.006). No significant differences were noted in duration of reported symptoms between groups, and clinical complications occurred too infrequently to analyze. However, 2 (11%) of 18 of the cancer patients with positive culture results were hospitalized during the illness and one patient developed a nosocomial infection. None of the control children was hospitalized. These findings suggest the need for further study of the immunologic response of immunosuppressed children to influenza infection and a clinical efficacy trial of the influenza vaccine in these patients.

Contribution of rhinoviruses to respiratory viral infections in childhood: a prospective study in a mainly hospitalized infant population

A prospective study was carried out to investigate the contribution of rhinoviruses to respiratory viral infections in children and to investigate the influence of age, passive smoking, and educational level of the head of the family on the clinical course of viral respiratory disease. Nasopharyngeal aspirates from 519 infants (90.8% inpatients, 9.2% outpatients) were screened for the presence of rhinoviruses, respiratory syncytial virus (RSV), adenoviruses, parainfluenza virus types 1, 2, 3, influenza virus types A and B, and enteroviruses by tissue culture isolation procedure, enzyme-linked immunosorbent assay, and/or indirect immunofluorescence method. The total detection rate was 42.4%. The rate decreased with increasing age. Higher detection rates were observed in specimens from children suffering from a more severe respiratory disease, and the highest rate of virus-positive specimens was found in those aged 0-6 months. Second to RSV (23.1%), rhinoviruses were the most frequently recovered pathogens found in 11.8% of children with acute respiratory tract infections (RTI). In the age group 0-6 months the majority of severe respiratory illnesses was due to RSV. In infants aged 6 months to 1 year a decrease in the number of severe illnesses caused by RSV and an increase in the number of children suffering from a more severe RTI caused by rhinoviruses was found. With the possible exception of one group of children infected with rhinoviruses, a negative effect of passive smoking on the incidence and severity of viral RTI could not be established. A beneficial effect of breast feeding on the severity of viral RTI could not be definitely demonstrated.

Respiratory viruses in children admitted to hospital in Edinburgh 1972-1985

The temporal incidence of respiratory viruses identified in children admitted to an Edinburgh hospital over a period of 14 years, 1972-1985, is described, Respiratory syncytial (RS) virus was identified most often, usually (but not in 1979 and 1985) with single peaks of activity in the winter months. Influenza virus infections were seen in the winter and spring but we failed to find evidence of interference between RS and influenza virus. Of the viruses studied, the parainfluenza viruses were the least predictable in their epidemiological behaviour. The results of this study are compared with those of others and the role of certain aspects of the weather is considered.

An evolutionary epidemiological mechanism, with applications to type A influenza

In this paper I develop a model that describes an evolutionary epidemiological mechanism and apply this model to the epidemiology of type A influenza. This evolutionary epidemiological model differs from the classical nonevolutionary epidemiological model which has been applied to diseases like measles, rubella, and whooping cough in having a novel mechanism which causes susceptible individuals to be introduced into the host population. In the nonevolutionary model, susceptibles are continually introduced into the host population by demographic processes: most hosts that die are immune, while newborn hosts are susceptible. In this evolutionary model, the susceptible class is continually replenished because the pathogen changes genetically, and hence immunologically, from one epidemic to the next, causing previously immune hosts to become susceptible. I derive formulae which describe how the equilibrium number of infected hosts, the interepidemic period, and the probability that a host will become reinfected depend on the rate of amino acid substitution in the pathogen, m, a parameter describing the effect of these substitutions on host immunity, gamma, as well as the host population size, N, and the recovery rate, r. To apply the model to influenza, I show how the nondimensional parameter epsilon = m gamma N/r2 may be estimated from four types of data. The methods are applied to several data sets, and I conclude that epsilon much less than 1; sampling variation and inconsistencies between the various data sets do not permit epsilon to be estimated more precisely. The evolutionary epidemiological model has no threshold host population size, in contrast to the nonevolutionary model.

Use of monoclonal antibodies for rapid detection of influenza A virus in nasopharyngeal secretions

Two monoclonal antibodies against influenza A virus were assessed for use as diagnostic reagents in an indirect immunofluorescence assay (IFA) of nasopharyngeal secretions. Monoclonal antibody IA-52, directed at an internal antigen, reacted with all influenza A tested. The high stability of this epitope permitted its use in a rapid IFA test, which gave results comparable to those obtained with polyclonal antibodies and viral isolation. The second monoclonal antibody, IA-279 was directed at a surface epitope (hemagglutinin); it reacted with almost all H3 subtype strains. Positive IFA using these monoclonal antibodies permitted rapid preliminary differentiation between the current two major subtypes of influenza A virus (H1N1, H3N2).

Monoclonal antibodies for the rapid diagnosis of influenza A and B virus infections by immunofluorescence

Mouse monoclonal antibodies, directed against antigenic sites on influenza A and B viruses and found to be type-specific in an immunoassay, were assessed for use as diagnostic reagents in an indirect immunofluorescence assay on nasopharyngeal secretions. The influenza A antibodies were directed against nucleoprotein or matrix protein antigens and the influenza B antibodies against nucleoprotein and haemagglutinin antigens. The influenza A anti-matrix monoclonal antibody was found to give a strong intranuclear particulate fluorescence in normal baboon kidney cells and cells from nasopharyngeal secretions negative for influenza A virus, including those from a patient infected with respiratory syncytial virus. Pools of the remaining monoclonal antibodies gave satisfactory results on 25 specimens from patients with influenza A H1N1 and H3N2 subtypes and 12 from patients with influenza B.

Respiratory virus infection in hospitalized children in Austria 1979-1982. Diagnosis by immunofluorescence

Nasal secretions from 349 Austrian children under six years of age who were hospitalized for respiratory illnesses were screened for the presence of respiratory syncytial virus (RSV), parainfluenza virus 1 and 3, adenovirus and influenza A virus over a period of four years by the immunofluorescence technique. 35% of the specimens were found to be positive for one of the five viruses investigated. RSV was detected in 31% of the nasal secretions and was thus the most frequently encountered causative agent of respiratory infections in the age group investigated. RSV infections occurred almost exclusively in the winter months and were mainly associated with bronchiolitis and pneumonia. Only sporadic infections were found with one of the other viruses investigated.

Viral infections of the respiratory tract in hospitalized children. A study from Oslo during a 90 months' period

A diagnosis of 979 respiratory viral infections was made in hospitalized children. Respiratory syncytial virus greatly out-numbered the other viruses: it caused 58% of the total virus infections and occurred in winter epidemics. Influenza A and B virus occurred during late winter and spring, rhinovirus had a seasonal distribution towards spring and autumn, whereas adenovirus types 1, 2 and 5 had no distinct seasonal distribution. Whereas respiratory syncytial virus were mainly associated with bronchiolitis and adenovirus type 7 with pneumonia, rhinovirus infections were most often found in children with episodes of acute bronchial asthma. The influenza A and B and adenovirus types 1, 2 and 5 infections often occurred with extrarespiratory symptoms, especially febrile convulsions.

A two year prospective study of hospital-acquired respiratory virus infection on paediatric wards

Over a 24 month period on six paediatric wards of different designs 169 cases of possible hospital-acquired respiratory virus infection were investigated. A variety of viruses was isolated from 82 cases, the most common being respiratory syncytial virus, influenza, parainfluenza, adenoviruses and rhinoviruses. A further 73 children developed respiratory symptoms between 3 and 300 days after administration but viruses were not demonstrable by the techniques used. These children were thought to have hospital-acquired infection nonetheless. Thirteen children were shown not to have acquired infection as the cause of their intercurrent illness. Most acquired infections occurred where toddlers were in cots in open wards. Children with trauma, including non-accidental injury, congenital malformations, mental retardation, failure to thrive or neoplasia were most likely to become infected. Almost 20% of children suffered from croup or lower respiratory tract illness as a result of their acquired infection. The figure was 41% if those less than 12 months old were considered alone. Most episodes settled quickly but in a few children investigations or surgery were delayed for a few days.

Seasonal pattern in childhood viral lower respiratory tract infections in Melbourne

Respiratory syncytial virus and parainfluenza viruses are the major pathogens in acute lower respiratory infection in infants and younger children. They show distinct seasonal patterns. An annual epidemic of respiratory syncytial virus infection is seen in Melbourne and this coincides with the coldest months of the year. Parainfluenza virus Type 1, the most frequent cause of laryngotracheobronchitis, occurs as an autumn epidemic every second year. Parainfluenza virus Types 2 and 3 are present most years and do not show a clear seasonal pattern.