Keiji Fukuda

The Impact of Influenza Epidemics on Hospitalizations

The traditional method for assessing the severity of influenza seasons is to estimate the associated increase (i.e., excess) in pneumonia and influenza (P&I) mortality. In this study, excess P&I hospitalizations were estimated from National Hospital Discharge Survey Data from 26 influenza seasons (1970-1995). The average seasonal rate of excess P&I hospitalization was 49 (range, 8-102) /100,000 persons, but average rates were twice as high during A(H3N2) influenza seasons as during A(H1N1)/B seasons. Persons aged <65 years had 57% of all influenza-related hospitalizations; however, the average seasonal risk for influenza-related P&I hospitalizations was much higher in the elderly than in persons aged <65 years. The 26 pairs of excess P&I hospitalization and mortality rates were linearly correlated. During the A(H3N2) influenza seasons after the 1968 pandemic, excess P&I hospitalizations declined among persons aged <65 years but not among the elderly. This suggests that influenza-related hospitalizations will increase disproportionately among younger persons in future pandemics.

Antibody Response in Individuals Infected with Avian Influenza A (H5N1) Viruses and Detection of Anti-H5 Antibody among Household and Social Contacts

The first documented outbreak of human respiratory disease caused by avian influenza A (H5N1) viruses occurred in Hong Kong in 1997. The kinetics of the antibody response to the avian virus in H5N1-infected persons was similar to that of a primary response to human influenza A viruses; serum neutralizing antibody was detected, in general, >/=14 days after symptom onset. Cohort studies were conducted to assess the risk of human-to-human transmission of the virus. By use of a combination of serologic assays, 6 of 51 household contacts, 1 of 26 tour group members, and none of 47 coworkers exposed to H5N1-infected persons were positive for H5 antibody. One H5 antibody-positive household contact, with no history of poultry exposure, provided evidence that human-to-human transmission of the avian virus may have occurred through close physical contact with H5N1-infected patients. In contrast, social exposure to case patients was not associated with H5N1 infection.

The epidemiology of chronic fatigue in San Francisco

Despite considerable research on chronic fatigue syndrome (CFS) and conditions associated with unexplained chronic fatigue (CF), little is known about their prevalence and demographic distribution in the population. The present study describes the epidemiology and characteristics of self-reported CF and related conditions in a diverse urban community. The study used a cross-sectional telephone screening survey of households in San Francisco, followed by interviews with fatigued and nonfatigued residents. Respondents who appeared to meet case definition criteria for CFS, based on self-reported fatigue characteristics, symptoms, and medical history, were classified as CFS-like cases. Subjects who reported idiopathic chronic fatigue (ICF) that did not meet CFS criteria were classified as ICF-like cases. Screening interviews were completed for 8,004 households, providing fatigue and demographic information for 16,970 residents. Unexplained CF was extremely rare among household residents <18 years of age, but was reported by 2% of adult respondents. A total of 33 adults (0.2% of the study population) were classified as CFS-like cases and 259 (1.8%) as ICF-like cases. Neither condition clustered within households. CFS- and ICF-like illnesses were most prevalent among women and persons with annual household incomes below

Influenza A among Patients with Human Immunodeficiency Virus: An Outbreak of Infection at a Residential Facility in New York City

40,000, and least prevalent among Asians. The prevalence of CFS-like illness was elevated among African Americans, Native Americans, and persons engaged in clerical occupations. Although CFS-like cases were more severely ill than those with ICF-like illness, a similar symptom pattern was observed in both groups. In conclusion, conditions associated with unexplained CF occur in all sociodemographic groups but appear to be most prevalent among women, persons with lower income, and some racial minorities.

Cruise ships: high-risk passengers and the global spread of new influenza viruses.

Although annual influenza vaccination is recommended for persons who are infected with human immunodeficiency virus (HIV), data are limited regarding the epidemiology of influenza or the effectiveness of influenza vaccination in this population. We investigated a 1996 outbreak of infection with influenza A at a residential facility for persons with AIDS. We interviewed 118 residents and employees, reviewed 65 resident medical records, and collected serum samples for measurement of influenza antibody titers. After controlling for history of smoking, influenza vaccination, and resident or employee status, in a multivariate model, HIV infection was not statistically associated with influenza-like illness (ILI). Symptoms and duration of ILI were similar for most HIV-infected and HIV-uninfected persons. However, 8 (21.1%) of 38 HIV-infected persons with ILI (vs. none of 15 HIV-uninfected persons) were either hospitalized, evaluated in an emergency room, or had ILI lasting > or = 14 days (P=.06). Vaccination effectiveness (VE) was similar for HIV-infected and HIV-uninfected persons. Vaccination was most effective among HIV-infected persons with CD4 cell counts of >100 cells/microL (VE, 65%; 95% CI, 36%--81%) or HIV type 1 virus load of <30,000 copies/mL (VE, 52%; 95% CI, 11%--75%). Providers should continue to offer influenza vaccination to HIV-infected persons.

Values for preventing influenza-related morbidity and vaccine adverse events in children

In 1997, passengers on North American cruises developed acute respiratory illnesses (ARIs); influenza was suspected. We reviewed 1 ships medical records for 3 cruises: cruise 1 (31 August to 10 September 1997), cruise 2 (11-20 September 1997), and cruise 3 (20-30 September 1997). Medically attended ARI was defined as any 2 of the following symptoms: fever (temperature, > or =37.8 degrees C) or feverishness, sore throat, cough, nasal congestion, chills, myalgia, and arthralgia. During cruise 2, we collected nasopharyngeal swabs for viral culture from people with ARI and surveyed passengers for self-reported ARI (defined as above except feverishness was substituted for fever). The outbreak probably began among Australian passengers on cruise 1 (relative risk, 3.3; 95% confidence interval, 1.89-5.77). Of 1284 passengers on cruise 2, 215 (17%) reported ARI, 994 (77%) were aged > or =65 years, and 336 (26%) had other risk factors for respiratory complications. An influenza strain not previously identified in North America was isolated. We concluded that an off-season influenza outbreak occurred among international travelers and crew on board this cruise ship.

Preparing for pandemic influenza: the need for enhanced surveillance

BackgroundInfluenza vaccination recently has been recommended for children 6–23 months old, but is not currently recommended for routine use in non-high-risk older children. Information on disease impact, costs, benefits, risks, and community preferences could help guide decisions about which age and risk groups should be vaccinated and strategies for improving coverage. The objective of this study was to measure preferences and willingness-to-pay for changes in health-related quality of life associated with uncomplicated influenza and two rarely-occurring vaccination-related adverse events (anaphylaxis and Guillain-Barré syndrome) in children.MethodsWe conducted telephone interviews with adult members selected at random from a large New England HMO (n = 112). Respondents were given descriptions of four health outcomes: uncomplicated influenza in a hypothetical 1-year-old child of their own, uncomplicated influenza in a hypothetical 14-year-old child of their own, anaphylaxis following vaccination, and Guillain-Barré syndrome. Uncomplicated influenza did not require a physicians visit or hospitalization. Preferences (values) for these health outcomes were measured using time-tradeoff and willingness-to-pay questions. Time-tradeoff questions asked the adult to assume they had a child and to consider how much time from the end of their own life they would be willing to surrender to avoid the health outcome in the child.ResultsRespondents said they would give a median of zero days of their lives to prevent an episode of uncomplicated influenza in either their (hypothetical) 1-year-old or 14-year-old, 30 days to prevent an episode of vaccination-related anaphylaxis, and 3 years to prevent a vaccination-related case of Guillain-Barré syndrome. Median willingness-to-pay to prevent uncomplicated influenza in a 1-year-old was

Influenza Outbreak Detection and Control Measures in Nursing Homes in the United States

175, uncomplicated influenza in a 14-year-old was

Fatiguing illness among employees in three large state office buildings, California, 1993: was there an outbreak?

100, anaphylaxis

Decreased antibody response among nursing home residents who received recalled influenza vaccine and results of revaccination, 1996-97

400, and Guillain-Barré syndrome