Contribution of influenza and respiratory syncytial virus to community cases of influenza-like illness: an observational study

Impact of severe disease caused by respiratory syncytial virus in children living in developed countries

Among industrialized nations, the rate of rehospitalization in the United States for respiratory syncytial virus (RSV) is approximately 30 per 1000, exceptions being noted for American Indians and Alaskan natives, two ethnic groups who tend toward higher rates of RSV hospitalization. In distinction Japan reports an admission rate of 60 per 1000 for RSV disease. Yet Japan ranks considerably lower than many of its western counterparts in premature births. Whether an RSV subtype, a new viral genotype or some other unifying characteristic exists that might explain the severity of adenovirus, parainfluenza and RSV infections in this region of Asia remains to be determined. Outcomes trials in the United States, Canada, United Kingdom, Denmark and Japan all identified crowding and exposure to tobacco smoke as significant and independent risk factors for disease severity of RSV. The epidemiology of RSV is largely consistent throughout Europe, with peak outbreaks occurring in December and January. In Europe RSV accounts for 42 to 45% of hospital admissions for lower respiratory tract infections in children younger than 2 years of age, and inpatient populations tend to be younger and to experience greater disease severity. For RSV bronchiolitis lengths of stay in European hospitals range from a low of 4 days to a high of 10 days. The Infección Respiratoria Infantil por Virus Respiratorio Sincitial Study Group in Spain conducted 2 prospective observational studies in 14 and 26 neonatal units, respectively, on nonprophylaxed neonates to determine hospitalization rates for respiratory syncytial viral illness during 2 consecutive RSV seasons. Throughout each respiratory season the study group followed premature infants of < or =32 weeks gestational age at birth, representing an annual birth cohort of approximately 100 000 infants. A total of 584 infants who were < or =32 weeks gestational age in the first season and 999 in the second season were followed at monthly intervals. The nonprophylaxed hospitalized group was compared with the nonprophylaxed, nonhospitalized group, and presumptive risk factors were determined for rehospitalization among premature infants. These independent variables, similar for both years, were identified as low gestational age, underlying chronic lung disease, living with school age siblings, exposure to tobacco smoke and a chronologic age of < 3 months at the onset of the RSV season.Stable, yet high rates of admission for RSV illness in Spain were observed in this premature group of < or =32 weeks gestational age: 13.4% for 1999; and 13.1% for the year 2000. Of those hospitalized during the 2 years of the study, 18 and 25%, respectively, were admitted to the intensive care unit. With the exception of higher rates of family allergy, multiple deliveries and a lower rate of neonatal morbidity, prognostic variables for high risk of hospital admission in the year 2000 compared with those of the 1999 sample. Findings from this comprehensive, prospective study served as the basis for the development of standards for the prevention of respiratory syncytial virus infection by the Spanish Society of Neonatology.

Recognizing influenza in older patients with chronic obstructive pulmonary disease who have received influenza vaccine

A substudy analysis was conducted to determine the clinical characteristics associated with symptomatic, laboratory-documented influenza (LDI) among 2215 veterans with chronic obstructive pulmonary disease who participated in Department of Veterans Affairs Cooperative Study 448 and who received trivalent inactivated influenza virus vaccine with or without intranasal live-attenuated, cold-adapted influenza vaccine. Of 585 evaluable first occurrences of acute respiratory illnesses, 94 (16%) were LDI. Respiratory symptoms of cough, sputum production, and dyspnea occurred in >90% of patients with LDI; 68% had documented or subjective fever, and 81% had myalgias. Stepwise logistic regression identified only fever and myalgia as being statistically associated with LDI. During the influenza outbreak period, the positive predictive value of fever and myalgia was 41%. Clinical criteria were poor predictors of LDI in these older, vaccinated patients with chronic lung disease. Additional studies are warranted to define optimal methods for the diagnosis of influenza among older persons with chronic obstructive pulmonary disease.

Mortality associated with influenza and respiratory syncytial virus in the United States

CONTEXT

Influenza and respiratory syncytial virus (RSV) cause substantial morbidity and mortality. Statistical methods used to estimate deaths in the United States attributable to influenza have not accounted for RSV circulation.

OBJECTIVE

To develop a statistical model using national mortality and viral surveillance data to estimate annual influenza- and RSV-associated deaths in the United States, by age group, virus, and influenza type and subtype.

DESIGN, SETTING, AND POPULATION

Age-specific Poisson regression models using national viral surveillance data for the 1976-1977 through 1998-1999 seasons were used to estimate influenza-associated deaths. Influenza- and RSV-associated deaths were simultaneously estimated for the 1990-1991 through 1998-1999 seasons.

MAIN OUTCOME MEASURES

Attributable deaths for 3 categories: underlying pneumonia and influenza, underlying respiratory and circulatory, and all causes.

RESULTS

Annual estimates of influenza-associated deaths increased significantly between the 1976-1977 and 1998-1999 seasons for all 3 death categories (P<.001 for each category). For the 1990-1991 through 1998-1999 seasons, the greatest mean numbers of deaths were associated with influenza A(H3N2) viruses, followed by RSV, influenza B, and influenza A(H1N1). Influenza viruses and RSV, respectively, were associated with annual means (SD) of 8097 (3084) and 2707 (196) underlying pneumonia and influenza deaths, 36 155 (11 055) and 11 321 (668) underlying respiratory and circulatory deaths, and 51 203 (15 081) and 17 358 (1086) all-cause deaths. For underlying respiratory and circulatory deaths, 90% of influenza- and 78% of RSV-associated deaths occurred among persons aged 65 years or older. Influenza was associated with more deaths than RSV in all age groups except for children younger than 1 year. On average, influenza was associated with 3 times as many deaths as RSV.

CONCLUSIONS

Mortality associated with both influenza and RSV circulation disproportionately affects elderly persons. Influenza deaths have increased substantially in the last 2 decades, in part because of aging of the population, underscoring the need for better prevention measures, including more effective vaccines and vaccination programs for elderly persons.

Virosome influenza vaccine in children

The use of vaccines for the prophylaxis of influenza in children is limited. This is despite high annual rates of influenza in children and despite the complications caused by influenza in children with chronic respiratory illnesses. The disease burden of influenza on infants and young children is reviewed and the potential of recommended influenza vaccination in healthy children, to reduce the direct and indirect health and socio-economic costs, is considered. Clinical experience with a virosome-formulated subunit influenza vaccine in children is presented. These clinical trials in children have shown a virosome-formulated subunit influenza vaccine to be immunogenic and well tolerated, indicating that it might be recommended for immunising healthy infants and children against influenza virus.

Human metapneumovirus as a cause of community-acquired respiratory illness

Human metapneumovirus (HMPV) is a recently identified Paramyxovirus first isolated from hospitalized children with acute respiratory tract infections (ARTI). We sought evidence of HMPV infection in patients who had visited general practitioners, had influenzalike illnesses (ILI), and had negative tests for influenza and Human respiratory syncytial virus (HRSV). As part of national virologic surveillance, sentinel general practices in England and Wales collected samples from patients of all ages with ILI during winter 2000-01. Reverse transcriptase-polymerase chain reaction (PCR) for HMPV, influenza A (H1 and H3), influenza B, and HRSV (A and B) was used to screen combined nose and throat swabs. PCR products from the HMPV-positive samples were sequenced to confirm identity and construct phylogenetic trees. Of 711 swabs submitted, 408 (57.3%) were negative for influenza and HRSV; HMPV was identified in 9 (2.2%) patients. HMPV appears to be associated with community-acquired ARTI. The extent of illness and possible complications related to this new human virus need to be clarified.

Respiratory tract reinfections by the new human Metapneumovirus in an immunocompromised child

The human Metapneumovirus (HMPV), a new member of the Paramyxoviridae family, has been recently associated with respiratory tract infections in young children. We report the case of a young, immunocompromised child who had severe lower respiratory tract infections during two consecutive winter seasons caused by genetically distinct HMPV strains.

Antioxidant enzymes in blood of patients with Friedreich's ataxia

BACKGROUND AND AIMS

Increased generation of reactive oxygen species and mitochondrial dysfunction may underlie the pathophysiology of Friedreich's ataxia, the most common inherited ataxia, due to GAA expansion in a gene coding for a mitochondrial protein (frataxin), implicated in the regulation of iron metabolism. Because iron overload would cause oxidative stress in Friedreich's ataxia, we investigated the enzyme antioxidant system in the blood of 14 patients by determining superoxide dismutase, glutathione peroxidase, and glutathione transferase catalytic activities. We also studied the glutathione S-transferase genotype polymorphism in order to evaluate its possible influence on enzyme activity.

METHODS

Blood samples were obtained from 14 unrelated patients with Friedreich's ataxia and 21 age matched healthy subjects. Antioxidant enzyme determinations were spectrophotometrically assayed using specific substrates; the glutathione S-transferase genotype polymorphism was analysed by endonuclease restriction mapping of exon 5 and 6 amplification products.

RESULTS

There was a significant elevation of the superoxide dismutase/glutathione peroxidase activity ratio (0.037 (0.01) v 0.025 (0.008) of controls) and an 83% rise of glutathione transferase specific activity (0.22 (0.1) v 0.12 (0.03) nmol/min/mg protein) in blood of patients with Friedreich's ataxia than in the controls. The genotype polymorphism of glutathione S-transferase enzyme did not show any relevant differences when compared to that of healthy subjects.

CONCLUSIONS

Data show an impairment in vivo of antioxidant enzymes in patients with Friedreich's ataxia and provide evidence of an increased sensitivity to oxidative stress, supporting a consistent role of free radical cytotoxicity in the pathophysiology of the disease.

The clinical diagnosis of influenza

Effective management of influenza depends on early recognition of influenza in the community and on rapid diagnosis. Early recognition is achieved by integrated clinical and laboratory based surveillance programmes in representative populations. The recent introduction of 'near patient tests' for influenza provide increased opportunities for surveillance but diagnosis remains largely clinically based. The combination of cough and fever in conditons of known local influenza virus circulation provide a useful indicator of diagnosis to guide management.

Influenza diagnosis and treatment: a view from clinical practice

Influenza is a descriptive term for respiratory epidemic disease presenting with cough and fever. Influenza viruses are probably the most important of the pathogens that cause this condition. Clinical influenza occurs almost every winter in England and Wales and the outbreaks last 8-10 weeks. In recent years, influenza B virus outbreaks have occurred in January and February, whereas influenza H3N2 virus outbreaks have generally started long before Christmas. Influenza H3N2 virus outbreaks pressurize health service resources in winter more than influenza B viruses, that do not have the same impact in elderly people. Infections with influenza H1N1 viruses are also usually less severe in their impact than those with influenza H3N2 viruses, but, unlike influenza B viruses, influenza H1N1 viruses have a pandemic potential along with influenza H3N2 viruses. A diagnosis of respiratory infection in primary care is based on the presenting symptoms set within the context of the current pattern of consultations of patients with similar illness. Measurement of temperature, inspection of the throat and examination of the chest or ears add a little to the diagnostic process, but in general these procedures do not help in identifying the organism. However, if it is known that influenza viruses are circulating in the community, the probability of influenza as the cause is greatly increased, as was shown in clinical trials of neuraminidase antivirals. Maximum confusion occurs when respiratory syncytial virus (RSV) and influenza cocirculate. Although RSV infection can occur throughout the winter in young children, it assumes more of an epidemic character just before Christmas in children and possibly in adults just after. During seven of the last 20 winters, influenza has been prevalent around Christmas/New Year. In routine virological surveillance of influenza-like illness in the community during the winters of 1997, 1998 and 1999, ca. 30% of swab specimens yielded influenza viruses and 20% RSV. Given the limitations for routine surveillance, including variations in the interval between illness onset and specimen capture, the quality of swab, delays in transport, the growth properties of virus culture methods, etc., these figures probably underestimate the impact of both viruses in the community. The impact of influenza is considered against the background of total respiratory infections presenting to general practitioners over the last 10 years and some comparisons are made with the 1969 pandemic experience. Lessons relevant to pandemic planning are drawn. Current options for investigation and treatment are compared with those available in 1969. These include near-patient tests for assisting with diagnosis, widespread use of vaccination as a preventive in patients at increased risk, the availability of amantadine and the newer neuraminidase inhibitor antivirals and changes in the delivery of health care. Major advances in the understanding of influenza and improvements in investigation and treatment have taken place over the last 30 years. However, there are many obstacles before these can be translated into effective management of influenza sufferers and control of major epidemics.