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...

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

The threat posed by the highly pathogenic H5N1 influenza virus requires public health authorities to prepare for a human pandemic. Although pre-pandemic vaccines and antiviral drugs might significantly reduce illness rates, their stockpiling is too expensive to be practical for many countries. Consequently, alternative control strategies, based on non-pharmaceutical interventions, are a potentially attractive policy option. School closure is the measure most often considered. The high social and economic costs of closing schools for months make it an expensive and therefore controversial policy, and the current absence of quantitative data on the role of schools during influenza epidemics means there is little consensus on the probable effectiveness of school closure in reducing the impact of a pandemic. Here, from the joint analysis of surveillance data and holiday timing in France, we quantify the role of schools in influenza epidemics and predict the effect of school closure during a pandemic. We show that holidays lead to a 20-29% reduction in the rate at which influenza is transmitted to children, but that they have no detectable effect on the contact patterns of adults. Holidays prevent 16-18% of seasonal influenza cases (18-21% in children). By extrapolation, we find that prolonged school closure during a pandemic might reduce the cumulative number of cases by 13-17% (18-23% in children) and peak attack rates by up to 39-45% (47-52% in children). The impact of school closure would be reduced if it proved difficult to maintain low contact rates among children for a prolonged period.

Estimating the impact of school closure on influenza transmission from Sentinel data

The report of the Institute of Medicine's Committee on Emerging Microbial Threats to Health in the United States, published in 1992, defines influenza virus as the prototype emerging infection (1). Pandemics of influenza have been recognized since earliest recorded history and, because of the mutability of the virus, still represent a formidable threat to the health of the nation. Although much progress has been made in describing the molecular aspects of the virus, in elucidating the epidemiology and modes of spread, and in developing methods for prevention and treatment, a rational strategy for control has not been established. The trends of modern society, including the increasing availability of rapid human transportation and the urbanization of the rapidly expanding human population, tend to facilitate the spread of influenza and increase morbidity. Modern medicine can reduce the mortality that resulted from complications of infection with influenza virus during earlier epidemics, but the cost of medical interventions has increased to the point that effective methods of epidemic control should be considered. This challenge provides an opportunity to develop, test, and have in place a strategy for control of interpandemic influenza before the next pandemic. Pandemics result from the emergence of an influenza A virus that is novel for the human population. Evidence for recycling of subtypes of influenza A after intervals of 60 years or more has been derived by determining antibody prevalence in elderly populations prior to the emergence of subtypes H2N2 in 1957 and H3N2 in 1968 (2, 3). A more ominous threat is the reservoir of 14 influenza A subtypes that persist in avian hosts (4). An avian virus can reassort with a human virus, as occurred in 1957 and 1968, to allow the creation of progeny that possess novel surface antigens with the potential to spread in human popu-

Emerging Infections: Pandemic Influenza

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

Background High attack rates of Influenzavirus among school-aged children tend to be expected to cause significant disruption of usual activities at school and at home. Objective To quantify the effect of influenza season on illness episodes, school absenteeism, medication use, parental absenteeism from work, and the occurrence of secondary illness in families among a cohort of children enrolled in an elementary school during the 2000-2001 influenza season. Design Prospective survey study. Setting Kindergarten through eighth grade elementary school in Seattle, Wash. Patients or other participants All children enrolled in the school were eligible for the study. Study participants were 313 children in 216 families. Main outcome measures The primary outcome measure was missed school days. Secondary outcomes measures included total illness episodes, febrile illness episodes, medication usage, physician visits, parental workdays missed, and secondary illnesses among family members of children in the study cohort. Differences between the rates of study events among participants when influenza was circulating and the event rates during the winter season when influenza was not circulating were used to calculate influenza-attributable excess events. Results Total illness episodes, febrile illness episodes, analgesic use, school absenteeism, parental industrial absenteeism, and secondary illness among family members were significantly higher during influenza season compared with the noninfluenza winter season. For every 100 children followed up for this influenza season, which included 37 school days, an excess 28 illness episodes and 63 missed school days occurred. Similarly, for every 100 children followed up, influenza accounted for an estimated 20 days of work missed by the parents and 22 secondary illness episodes among family members. Conclusion Influenza season has significant adverse effects on the quality of life of school-aged children and their families.

https://jamanetwork.com/journals/jamapediatrics/articlepdf/204004/poa20122.pdf

Illness among schoolchildren during influenza season: effect on school absenteeism, parental absenteeism from work, and secondary illness in families.

Since influenza A/H1N1 viruses reappeared during the 1977-1978 season, this subtype has contributed 27% of 6,609 documented influenza infections of persons with acute respiratory disease presenting to clinics serving as surveillance sites of the Influenza Research Center in Houston for the 12-year period ending June 1989. Wide differences in the distribution of H1N1 viruses occurred by age group: more than 50% of H1N1 infections were detected among persons aged 10-34 years, compared with 28% for influenza A/H3N2 and 35% for influenza B. Over age 35 years, the contribution of H1N1 viruses dropped to only 4%, compared with 20% and 16% for influenza A/H3N2 and influenza B, respectively. When birth dates of persons with positive cultures were examined, it was found that most of the H1N1-positive persons were born after 1950. Concurrently, longitudinal studies of families and other adults under intensive surveillance for infection, including cultures of all respiratory illnesses and tests for serum antibody rise over the respiratory disease season, revealed appreciable infection rates for adults born before 1950. Furthermore, the annual peak of hospitalization of older persons with pneumonia and other acute respiratory illnesses was significantly correlated with the peak of H1N1 virus activity in 1978-1979, a year when H1N1 viruses were the only influenza viruses prevalent. These observations indicate that many persons infected with influenza A/H1N1 viruses that circulated from 1946 through 1953 have immunity which has persisted for more than 25 years but this immunity is not complete. Reinfection that may result in serious illness in older vulnerable adults does occur but with lower frequency than with influenza A/H3N2 infection. Currently prevalent H1N1 variants are antigenically different from those that circulated in the 1950s; however, older adults readily acquire immunity to these new variants--perhaps as a result of immunologic priming that occurred in childhood.

Age distribution of patients with medically-attended illnesses caused by sequential variants of influenza A/H1N1 : comparison to age-specific infection rates, 1978-1989

P A Piedra

Papers

Age distribution of patients with medically-attended illnesses caused by sequential variants of influenza A/H1N1 : comparison to age-specific infection rates, 1978-1989