Influenza A and B virus infection in infants and young children during the years 1957-1976

Accumulation of mini-plasmin in the cerebral capillaries causes vascular invasion of the murine brain by a pneumotropic influenza A virus: implications for influenza-associated encephalopathy

The infectivity and pathogenicity of influenza virus are primarily determined by host cellular trypsin-type processing proteases which cleave the viral membrane fusion glycoprotein hemagglutinin (HA). Therefore the distribution of the processing protease is a major determinant of the infectious organ tropism. The common epidemic human influenza A virus is pneumotropic and the HA processing proteases tryptase Clara, mini-plasmin, tryptase TC30 and ectopic anionic trypsin have all been isolated from mammalian airways. However, the pneumotropic influenza virus occasionally causes severe brain edema, particularly in children presenting with Reye's syndrome treated with aspirin, or in children with influenza-associated encephalopathy without antipyretic treatment. We have observed that, after influenza virus infection, the accumulation of mini-plasmin in the cerebral capillaries in mice with a congenital or acquired abnormality of mitochondrial beta-oxidation mimicking the pathological findings of Reye's syndrome, causes an invasion and multiplication of the pneumotropic influenza virus at these same locations. From these findings, we hypothesize that the accumulated mini-plasmin modifies the brain capillaries from a non-permissive to a permissive state, thereby allowing multiplication of pneumotropic influenza virus. In addition, mini-plasmin proteolytically destroys the blood-brain barrier. These pathologic findings, consistent with encephalopathy in mice with a systemic impairment of beta-oxidation, may have implications for human influenza encephalopathy.

Influenza A and B virus infections in children

To obtain data on the clinical manifestations of infection, the age distribution, and the underlying conditions of children with influenza severe enough to lead to hospital referral, we performed a retrospective study of children treated at Turku University Hospital (Turku, Finland) in 1980-1999. Influenza A or B antigen was detected in the nasopharyngeal aspirates of 683 of the 15,420 children studied. The median age of children with influenza A was 2.0 years (n=544), and that of children with influenza B was 4.2 years (n=139) (P<.001). One-fourth of the children had an underlying medical condition. High fever, cough, and rhinorrhea were the most frequently recorded symptoms. Acute otitis media developed in 24% of the children, and pneumonia developed in 9% of the children. The study shows that the majority of patient hospitalizations for pediatric influenza involve previously healthy infants and young children. Laboratory confirmation of influenza is particularly important for children because the clinical presentation of the infection is less characteristic than that seen in adults.

Influenza-related hospitalizations among children in Hong Kong

BACKGROUND

It has been difficult to define the burden of influenza in children because of confounding by the cocirculation of respiratory syncytial virus (RSV). In Hong Kong, China, the influenza and RSV infection seasons sometimes do not overlap, thus providing an opportunity to estimate the rate of influenza-related hospitalization in a defined population, free from the effects of RSV.

METHODS

In a retrospective, population-based study, we estimated the influenza-associated excess rate of hospitalization among children 15 years old or younger in the Hong Kong Special Administrative Region from 1997 to 1999. Data from a single hospital with intensive use of virologic analyses for diagnosis were obtained to define and adjust for underestimation of the model.

RESULTS

Peaks of influenza and RSV infection activity were well separated in 1998 and 1999 but overlapped in 1997. The adjusted rates of excess hospitalization for acute respiratory disease that were attributable to influenza were 278.5 and 288.2 per 10,000 children less than 1 year of age in 1998 and 1999, respectively; 218.4 and 209.3 per 10,000 children 1 to less than 2 years of age; 125.6 and 77.3 per 10,000 children 2 to less than 5 years of age; 57.3 and 20.9 per 10,000 children 5 to less than 10 years of age; and 16.4 and 8.1 per 10,000 children 10 to 15 years of age.

CONCLUSIONS

In the subtropics, influenza is an important cause of hospitalization among children, with rates exceeding those reported for temperate regions.

Influenza vaccines in children

Influenza is a common disease of childhood. Young children and children with high-risk medical conditions are at increased risk of being hospitalized when infected with influenza virus. Children of all ages have excess physician visits and receive excess antibiotic prescriptions during influenza season. The safety, immunogenicity, and efficacy of influenza vaccines in children are described in this review. Clinical trials and postlicensure experience have demonstrated that trivalent inactivated influenza vaccine is well-tolerated in children. Efficacy of the inactivated vaccine also has been demonstrated in numerous clinical trials. In comparison to trivalent inactivated influenza vaccine, investigational cold-adapted, live-attenuated influenza vaccine (LAIV) has the advantage of an intranasal route of administration. A large clinical trial demonstrated the tolerability and efficacy of the trivalent live, attenuated product in children 15 to 71 months of age. Pending information on safety and coadministration of this vaccine with other childhood vaccines will determine if it is licensed and recommended for use in children, including possible expanded indications for routine yearly administration to young children.

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.

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.

Influenza vaccine: issues and opportunities

Several recent developments offer opportunities to improve the diagnosis, treatment, and prevention of influenza. Rapid diagnostic tests assist in selecting patients for antiviral therapy and avoid some antibiotic use. The neuraminidase inhibitors now offer therapeutic options with potentially fewer side effects than the traditional drugs, albeit at greater cost. Inactivated influenza vaccine is now recommended annually for all persons aged 50 and older and younger adults and children (aged 6 months and older) who have underlying risk factors for the severe complications of influenza. This includes pregnant women who are in their second or third trimesters during influenza season.

Protection against influenza B virus infection by immunization with DNA vaccines

Protection against a lethal influenza B virus infection was examined in BALB/c mice immunized with plasmid DNAs encoding hemagglutinin (HA), neuraminidase (NA and NB) and nucleoprotein (NP) from the B/Ibaraki/2/85 virus. Each DNA vaccine was administered twice, 3 weeks apart, at a dose of 1 microg per mouse by particle-mediated DNA transfer to the epidermis (gene gun) or at a dose of 30 microg per mouse by electroporation into the muscle. Three weeks after the second vaccination, the mice were challenged with a lethal dose of homologous virus. HA and NA DNAs conferred complete protection against the lethal viral challenge, whereas NB and NP DNAs failed to provide protection against infection. Furthermore, protection in different strains of mice, BALB/c, B10 and C3H, immunized with HA and NA DNAs was compared. Both HA and NA DNAs conferred complete protection against the lethal challenge in all the tested mouse strains. These results suggest that both the HA and NA molecules can be used as vaccine components to provide effective protection against influenza B virus infection.

The burden of influenza illness in children with asthma and other chronic medical conditions

OBJECTIVE

Although influenza immunization is recommended for children with high-risk medical conditions, the majority of such children do not receive influenza vaccine. This study was designed to measure the burden of influenza among children with asthma and other chronic medical conditions.

STUDY DESIGN

We performed a retrospective cohort study of children younger than 15 years with medically treated asthma or other chronic medical conditions enrolled in the Tennessee Medicaid program from 1973 to 1993. We determined rates of hospitalization for acute cardiopulmonary disease, outpatient visits, and antibiotic courses throughout the year. Annual differences between event rates when influenza virus was circulating and event rates during winter months when there was no influenza in the community were used to calculate influenza-attributable morbidity.

RESULTS

Influenza accounted for an average of 19, 8, and 2 excess hospitalizations for cardiopulmonary disease yearly per 1000 high-risk children aged <1 year, 1 to <3 years, and 3 to <15 years, respectively. For every 1000 children, an estimated 120 to 200 outpatient visits and 65 to 140 antibiotic courses were attributable to influenza annually.

CONCLUSIONS

Children younger than 15 years with asthma and other chronic medical conditions experience substantial morbidity requiring inpatient and outpatient care during influenza season. More effective targeting of this population for annual influenza immunization is warranted.

Use of monoclonal antibodies for rapid diagnosis of respiratory viruses in a community hospital

An indirect fluorescence antibody (IFA) procedure was used for the rapid detection of respiratory viruses in direct clinical specimens and for determining the epidemiology of viruses in a community hospital setting. Viral respiratory diseases were monitored for 10 consecutive respiratory seasons. The Bartels Viral Respiratory Screening and Identification Kit is an IFA method that contains pooled and individual monoclonal antibodies for seven common respiratory viruses. Compared with 8,670 conventional tube cell cultures, IFA staining of direct patient specimens had an overall sensitivity of 84.2% and a specificity of 87.7%. Yearly epidemics of respiratory syncytial virus were seen with alternating short and long intervals between successive periods when virus was isolated. Epidemics following short intervals were more severe. Influenza A virus epidemics occurred yearly, and influenza B virus activity was seen generally every other year. When influenza A and influenza B viruses were cocirculating in a given season, the months of peak activity of one virus were always within 1 month of the peak activity of the other virus. Parainfluenza virus type 1 was detected in the autumn of odd-numbered years, and parainfluenza type 2 virus was seen usually in the autumn of even-numbered years. Parainfluenza type 3 virus and adenovirus were the most ubiquitous agents, with peak incidence occurring in the late winter to spring.

The effect of influenza on hospitalizations, outpatient visits, and courses of antibiotics in children

BACKGROUND

Despite high annual rates of influenza in children, influenza vaccines are given to children infrequently. We measured the disease burden of influenza in a large cohort of healthy children in the Tennessee Medicaid program who were younger than 15 years of age.

METHODS

We determined the rates of hospitalization for acute cardiopulmonary conditions, outpatient visits, and courses of antibiotics over a period of 19 consecutive years. Using the differences in the rates of these events when influenzavirus was circulating and the rates from November through April when there was no influenza in the community, we calculated morbidity attributable to influenza. There was a total of 2,035,143 person-years of observation.

RESULTS

During periods when influenzavirus was circulating, the average number of hospitalizations for cardiopulmonary conditions in excess of the expected number was 104 per 10,000 children per year for children younger than 6 months of age, 50 per 10,000 per year for those 6 months to less than 12 months, 19 per 10,000 per year for those 1 year to less than 3 years, 9 per 10,000 per year for those 3 years to less than 5 years, and 4 per 10,000 per year for those 5 years to less than 15 years. For every 100 children, an annual average of 6 to 15 outpatient visits and 3 to 9 courses of antibiotics were attributable to influenza. In winter, 10 to 30 percent of the excess number of courses of antibiotics occurred during periods when influenzavirus was circulating.

CONCLUSIONS

Healthy children younger than one year of age are hospitalized for illness attributable to influenza at rates similar to those for adults at high risk for influenza. The rate of hospitalization decreases markedly with age. Influenza accounts for a substantial number of outpatient visits and courses of antibiotics in children of all ages.

A novel influenza subunit vaccine composed of liposome-encapsulated haemagglutinin/neuraminidase and IL-2 or GM-CSF. I. Vaccine characterization and efficacy studies in mice

The aim of this study was to improve the potency of the currently used influenza subunit vaccines, which are of relatively low efficiency in high-risk groups. Influenza A virus (Shangdong/9/93) haemagglutinin/neuraminidase (H3N2), granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-2 (IL-2) were encapsulated, each separately or combined, in multilamellar vesicles composed of dimyristoyl phosphatidylcholine. BALB/c mice were immunized once, i.p. or s.c., with 0.05-2.0 microg HN administered either as free antigen (F-HN), adsorbed to aluminum hydroxide (Al-HN), or encapsulated in liposomes (Lip-HN), separately or together with 1 x 10(2)-4.5 x 10(4) units of free or encapsulated cytokines. Serum antibodies were assayed on days 11-360 by the haemagglutination-inhibition (HI) test and ELISA. Protective immunity against intranasal virus challenge was determined at 9-14 months post-vaccination. The following results were obtained: (1) The efficiency of encapsulation in liposomes was 95, 90 and 38% for HN, IL-2 and GM-CSF, respectively, and the liposomal preparations were highly stable as an aqueous dispersion for > 2 months at 4 degrees C. (2) Following immunization with 0.5 microg Lip-HN, there was an earlier, up to 50-fold stronger, and 3-5 times longer response than that obtained with nonliposomal HN. (3) Coimmunization with free cytokines further increased the response 2-20 times and the two cytokines had an additive effect. (4) Liposomal cytokines were 2-20 times more effective than the free cytokines and their stimulatory effect was more durable. (5) A 100% seroconversion (HI titer > or = 40) was achieved with only 10-25% of the routinely used antigen dose, by encapsulating either antigen or cytokine. (6) The level of protection following vaccination with the combined liposomal vaccines was 70-100% versus 0-25% in mice immunized with Al-HN alone, and no toxicity was observed. In conclusion, our animal experiments show that the liposomal vaccines are superior to the currently used influenza vaccines, increasing the response by 2-3 orders of magnitude in mice. This approach may also prove valuable for subunit vaccines against other microorganisms.

Evaluation of bivalent live attenuated influenza A vaccines in children 2 months to 3 years of age: safety, immunogenicity and dose-response

1126 children, 2 months to 3 years old, received a single intranasal dose of 10(4), 10(6), or 10(7) TCID50 of cold adapted (ca) A/Kawasaki/9/86 (H1N1) and A/Beijing/352/89 (H3N2) or placebo, in a double blind, placebo-controlled, safety and immunogenicity trial. No reactogenicity attributable to vaccine was demonstrated. A single bivalent 10(6) or 10(7) dose produced high rates of seroconversion to H1N1 (77%) and H3N2 (92%) in seronegative children > 6 months old; serologic responses were lower to H1N1 (P < 0.001) and H3N2 (P = 0.01) in younger infants. A single 10(6) dose of bivalent ca influenza A vaccine can be immunogenic in children, but response is age dependent.

Use of PCR-enzyme immunoassay for identification of influenza A virus matrix RNA in clinical samples negative for cultivable virus

Influenza A virus infections are a major cause of morbidity and mortality worldwide. Standard diagnostic methods either are not efficient in identifying infected individuals in a timely manner or lack sensitivity. We developed a PCR-enzyme immunoassay (PCR-EIA) for the detection of influenza A virus RNA in respiratory secretions. A reverse transcription PCR was performed with oligonucleotide primers directed at a highly conserved area of the influenza A matrix gene. Amplified DNA was identified by hybridization in solution to a nested biotinylated RNA probe and quantitated in an EIA. PCR-EIA detected small quantities of RNA from the three prevalent subtypes of human influenza A virus. Influenza B and C, parainfluenza, measles, mumps, and respiratory syncytial viruses tested negative. The potential efficiency of PCR-EIA for use in clinical diagnosis was determined by testing 90 nasal wash specimens obtained daily over a 10-day period from nine human volunteers infected with influenza A virus. Thirty-seven of the postinfection samples had detectable influenza A virus RNA by PCR-EIA, whereas only 26 postinfection samples were positive by culture. PCR-EIA was particularly efficient for the identification of influenza A virus in samples obtained more than 4 days after infection. Seventeen of 45 such samples were positive, whereas virus was cultivated from 4 samples (P < 0.00005). All preinfection samples from volunteers subsequently infected with influenza A virus were negative by PCR-EIA, as were samples from a volunteer infected with parainfluenza virus type 3. Nucleic acid amplification techniques represent important tools for the timely and sensitive diagnosis of influenza A virus infections and, therefore, their management and control.

Cross-protection against influenza B type virus infection by intranasal inoculation of the HA vaccines combined with cholera toxin B subunit

The relationship between the antibody responses to various influenza B type virus HA vaccines and protection against live B virus infection was investigated in Balb/c mice which had been inoculated intranasally with a combination of the HA vaccines and B subunit of cholera toxin (CTB) 4 weeks previously. The inoculation of HA vaccine, prepared from B/Ibaraki/2/85 (B/Ibaraki), B/Nagasaki/1/87 (B/Nagasaki) or B/Aichi/5/88 (B/Aichi) viruses, combined with CTB induced high levels of both nasal IgA and serum HI antibodies to any of B/Ibaraki, B/Nagasaki and B/Aichi viral antigens. Simultaneous inoculation of each CTB-combined HA vaccine provided complete protection against B/Ibaraki virus infection which is demonstrated by both rapid clearance of pulmonary virus and complete survival. On the other hand, the inoculation of HA vaccine prepared from B/Yamagata/16/88 (B/Yamagata) virus together with CTB induced only a low level of nasal IgA antibodies, cross-reactive to B/Ibaraki, B/Nagasaki and B/Aichi viral antigens and protected only partially against B/Ibaraki virus challenge. The involvement of the B type virus-specific immunity in this protection was suggested by the absence of protection against B/Ibaraki virus infection in mice previously inoculated with both A/PR/8/34 (H1N1) virus HA vaccine and CTB. These results suggest that antibodies to various influenza B viruses are cross-reactive to each B type virus antigens and that cross-protection against B virus infection could be conferred depending on the degree of B type virus cross-reactive immunity including secretory IgA antibodies.

Role of upper respiratory tract infection in the deaths occurring in neonatal ferrets infected with influenza virus

Passive immunization of ferret neonates by colostrally-derived anti-influenza virus IgG did not entirely prevent infection when mothers were immunized with 1 or 2 doses of formalin inactivated vaccine with adjuvant (alhydrogel). Influenza virus replication was almost completely prevented in the lower respiratory tract but only slightly reduced in the upper respiratory tract leading to deaths in about 50% of the neonates. Such neonates showed at most only minor lesions in the lower respiratory tract but moderate to severe inflammatory changes in the upper respiratory tract of most animals. This supports previous results suggesting that deaths, reminiscent of the human sudden infant death syndrome (SIDS), may arise purely as a result of upper respiratory tract infection, possibly following obstruction of the airways.

Current approaches to the development of vaccines effective against parainfluenza and respiratory syncytial viruses

Vaccines against parainfluenza (PIV) and respiratory syncytial viruses (RSV) that are currently being developed include both live and subunit vaccines. Candidate live PIV vaccines that have been found to be attenuated and efficacious in rodents or primate models are (1) cold-adapted, temperature-sensitive mutants of PIV-type 3 that have been serially passaged at low temperature (20 degrees C) in simian kidney tissue culture; (2) protease-activation mutants (PIV-1-Sendai), which have mutations that decrease the cleavability of their F glycoprotein by host cell protease; (3) an animal virus, bovine PIV-3 virus, which is antigenically related to the human PIV-3 virus, and (4) vaccinia recombinant viruses bearing RSV or PIV-3 glycoproteins. Subunit RSV and PIV-3 viruses are being produced and evaluated as immunogens. A major concern with these vaccines is the possibility of disease potentiation following virus infection as occurred previously with formalin-inactivated measles and RSV vaccines. Studies indicate that PIV-3 and RSV glycoprotein vaccines are immunogenic and efficacious in animals but insufficient data exist to estimate their capacity to potentiate disease. However, since a cotton rat model is available to detect potentiated disease resulting from infection of cotton rats previously immunized with formalin-inactivated RSV vaccine, it is now possible to systematically evaluate new vaccines in experimental animals for disease potentiation before studies are initiated in humans. It is likely within the next several years that one or more of these PIV or RSV vaccines will be tested in humans for safety and immunogenicity.

Surveillance of respiratory viral infections by rapid immunofluorescence diagnosis, with emphasis on virus interference

During the 7-year period from September 1978 to August 1985, smear specimens of nasopharyngeal secretions from 3132 patients mainly hospitalized children, taken in different regions in Norway, were examined for respiratory viruses by the rapid immunofluorescence (IF) technique. A positive diagnosis for respiratory syncytial virus (RSV), parainfluenza virus type 1, 2 and 3 or influenza A and B virus was made for 896 patients (29%). The greatest prevalence for all these viruses was observed during the colder months with only sporadic cases during the summer months. A relative increase in parainfluenza virus activity, involving several parainfluenza virus types, was observed in every second autumn and during these periods only sporadic cases of RSV infection were diagnosed. Also both RSV and parainfluenza viruses were less frequently found during influenza virus epidemics and regional differences in RSV activity were observed. During the four autumn periods 1982-85 the monthly number of positive virus identifications by IF followed an epidemic curve, while the corresponding number of negative samples was relatively constant. The results of this study suggest interference between RSV, parainfluenza viruses and influenza virus in reaching their epidemiological peaks. It is suggested that interferon might be a mediator of this effect.

Simultaneous infections with different enteric and respiratory tract viruses

Infants and young children with rotavirus (RV) or visualized adenovirus in their stools were tested for the simultaneous presence of a respiratory viral pathogen in their upper respiratory tract. Overall, at least 10.7% of 484 study subjects had such dual infections, including 8.3% of 385 RV-positive gastroenteritis patients and 24.3% of 37 RV-positive respiratory disease patients. Respiratory syncytial virus was present in 34.1% of 41 dual infections with RV and at least 40% of the 12 to 15 dual infections with visualized fecal adenovirus. Other pathogens found in the respiratory tract of patients with RV or visualized fecal adenovirus infections included influenza viruses, adenoviruses, parainfluenza viruses, rhinoviruses, and a cytomegalovirus.

[Inactivated vaccine against trivalent influenza. Comparative study of the immune response by hemagglutination inhibition and simple radial hemolysis methods]

A vacina inativada contra gripe, trivalente, preparada no Instituto Butantan, contendo 200 unidades hemaglutinantes de cada uma das cepas de virus Influenza A/SP/1/80 (H3N2), A/SP/1/78 (H1N1) e B/England/847/73, foi administrada em 110 voluntários humanos adultos, sendo que 62 receberam uma dose de vacina e 48 duas doses, com intervalo de 21 dias. A resposta de anticorpos específicos para influenza foi analisada comparativamente pelos testes de Inibição da Hemaglutinação (IH) e Hemólise Radial Simples (HRS). Ocorreu aumento significativo do teor de anticorpos nos indivíduos vacinados, correspondente a um aumento de 4 vezes ou mais nos títulos obtidos pelo teste IH e a um aumento de 3,0 mm ou maior no diâmetro das zonas de hemólise pelo teste HRS. Os métodos demonstraram correlação satisfatória entre si.

Effects of social and family factors on viral respiratory infection and illness in the first year of life

A total of 131 infants were monitored from birth through the first year of life for respiratory viral infection and illness and evaluated for the relationship that these had to certain social and familial factors. The results showed no general patterns of association between viral infection and the study factors, but there were several significant individual associations. Excess influenza virus infection was found for black infants, infants with at least one sibling, and especially those with school age siblings. Rhinovirus infection rates were highest among girls attending daycare. In addition, significantly higher rates of lower respiratory disease (LRD) were seen in daycare infants and low socioeconomic infants and a definite trend to increasing amounts of LRD was seen with increasing family size. Protection from LRD seen in girls was apparently lost in daycare. No convincing differences for viral infection or respiratory illness were seen with parental smoking as an isolated factor.

Pediatric viral gastroenteritis during eight years of study

During the period January 1974 through July 1982, fecal samples from 1,537 pediatric inpatients with gastroenteritis were tested for enteric viruses by electron microscopic and rotavirus enzyme-linked immunosorbent assay techniques. Rotaviruses were detected in 34.5% of these patients, enteric adenoviruses were detected in 4.7%, approximately 27-nm viruses were detected in 1.6%, and at least one of these agents was found in 40.1% of the study subjects. Three infections were by an apparently new agent which morphologically is a rotavirus, but which failed to react in the rotavirus enzyme-linked immunosorbent assay. During the first 8 calendar years of study, rotaviruses were detected in 39.0% of 577 patients in the even-numbered years and 30.3% of 702 patients in the odd-numbered years. Adenoviruses were found in all calendar months. Rotaviruses were found in inpatients in November through July, whereas approximately 27-nm viruses were found in October through June. The percentage of patients who had a demonstrated viral infection rose steadily from 7.4% in September to 72.0% in January and then steadily declined to 2.9% in August. Viral infection was especially common in study subjects who were 7 through 24 months of age; 61% of such children had one or more enteric viruses. Rotavirus-infected patients tended to be younger during the months of greatest rotavirus activity than at the beginning and end of the rotavirus season, presumably because of a greater exposure to virus at the height of the rotavirus outbreak.

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.

Impact of type A influenza on children: a retrospective study

Excess morbidity was studied during influenza A epidemics (1968-69, 1972-73) among children in a large prepaid group practice program. Excess rates of hospitalization for influenza-related conditions, primarily pneumonia and bronchitis, ranged from 5 per 10,000 (95 per cent confidence limits (CL): 1 to 9) for non-high-risk children to 29 per 10,000 (95 per cent CL: 5 to 53) for children with high-risk conditions. The relative increases in hospitalization rates were greatest for 5-14 year old boys: 278 per cent and 104 per cent increases for high-risk and non-high-risk boys, respectively. The absolute increase was greatest for 0-4 year olds. The excess rate of ambulatory medical care contacts, 2.6 per 100 (95 per cent CL: -1.6 to 6.8 per 100) was not statistically significant. Excess hospitalization rates among 0-14 year olds during epidemics were three to five times larger than those for persons between 15 and 64 years of age but only one-fifth the rate of persons over age 65.

Observations on the seasonal variation of the most common acute pediatric diseases in the Helsinki area (Finland)

Seasonal variations in the incidence of the most common acute diseases in childhood during the inter-epidemic year 1978 were investigated using a sample of 7,068 walk-in patients attending. Aurora Hospital, Helsinki. At least seven out of the ten most common diseases were of infectious origin. Generally, boys and the younger groups were affected most often. The clearest seasonal difference in both sexes was observed in patients with gastroenteritis and otitis media. Among boys, there was also a marked fluctuation in the incidence of asthmatic bronchitis and asthma, pneumonia, and laryngitis, whereas, among girls, marked variations were observed only in urinary tract infections and acute upper respiratory infections. Children between 1 and 3 years of age appeared to be most prone to the common cold syndrome all the year round.