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Update: Influenza Activity -- United States, 1989

The first laboratory-confirmed outbreaks of influenza in the United States during the 1989-90 influenza season have been reported to CDC. The first outbreak occurred in a day-care center in Colorado in November and involved 24 children 6 weeks- 10 years of age. Influenza A(H3N2) was isolated from the only culture taken, which was from a 5-year-old with sickle cell anemia who was hospitalized for influenza.

During the week of December 4, an influenza A(H3N2) outbreak began in a Minnesota nursing home. Four residents and two employees have developed influenza-like illnesses. Influenza A(H3N2) has been isolated from one patient as of December 18.

From October 1 to December 18, CDC received reports of 42 culture-confirmed influenza A cases from 19 states. Of the 42 isolates, 16 were influenza A(H3N2), and three were influenza A(H1N1); 23 isolates have not been subtyped. States reporting isolates were Alabama, Alaska, Arizona, California, Connecticut, Colorado, Georgia, Hawaii, Massachusetts, Michigan, Minnesota, Missouri, Montana, New Mexico, North Carolina, Texas, Utah, Washington, and Wisconsin. As of December 18, all U.S. influenza A(H3N2) isolates characterized at CDC have been similar to the A/Shanghai/11/87-like virus antigen contained in the 1989-90 influenza vaccine. The A(H1N1) isolates are similar to the A/Taiwan/1/86-like vaccine antigen.

For the week ending December 9, sporadic influenza-like illness activity was reported by 20 states (Alabama, Alaska, Arizona, Delaware, Georgia, Hawaii, Kentucky, Maine, Michigan, Nevada, New Hampshire, New Mexico, New York, Ohio, Oklahoma, Rhode Island, South Dakota, Tennessee, Utah, and West Virginia) and Puerto Rico; two states (Massachusetts and Montana) reported regional activity.* For the same week, sentinel family practice physicians reported that 4.4% of patient visits were for influenza-like illnesses. During the 4 previous weeks, influenza-like illnesses generally increased, accounting for 2.6%, 3.1%, 4.5%, and 4.3% of visits, respectively. Reported by: P Graves, RE Hoffman, MD, Colorado Dept of Health. J Degelau, MD, MB Grimm, MT Osterholm, PhD, Minnesota Dept of Health. State and territorial health department epidemiologists and state laboratory directors. WHO Collaborating Laboratories. Sentinel Physicians of the American Academy of Family Practice. Epidemiology Office and Influenza Br, Div of Viral and Rickettsial Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Because influenza activity is currently increasing in the United States, health-care providers should consider options that can prevent or reduce the impact of influenza infection; these include 1) immunoprophylaxis with influenza vaccine and 2) chemoprophylaxis or therapy with amantadine. Annual vaccination of persons at increased risk for complications of influenza infection is the single most important measure available to reduce influenza-related morbidity and mortality. Amantadine may be used in conjunction with vaccination to prevent and control outbreaks of influenza A in institutional settings such as nursing homes and chronic-care facilities, for temporary prophylaxis until antibody develops in high-risk persons immunized after the start of the influenza season, for prophylaxis in immunodeficient persons, and for prophylaxis in high-risk persons for whom vaccine is contraindicated (1,2).

Even though infections caused by influenza A viruses have been confirmed, continued culturing of patients with influenza-like illness is encouraged. Efforts to isolate influenza will assist in identifying areas where influenza viruses are circulating and in determining the specific types/subtypes. Throughout the influenza season, CDC receives reports of influenza activity and isolates from state and local health departments and from sentinel physicians. This information is updated weekly and is available by telephone (CDC Disease Information Hotline, Influenza Update (404-332-4555)), through the CDC Information Service on the Public Health Network electronic bulletin board, and by periodic updates in the MMWR. More detailed information on local influenza activity is available from state or local health departments.


  1. ACIP. Prevention and control of influenza: part 1, vaccines. MMWR 1989;38:297-8,303-11.

  2. ACIP. Prevention and control of influenza. MMWR 1988;37:361-4,369-73.

*Levels of activity are: 1) Sporadic--sporadically occurring cases of influenza-like illness or culture-confirmed influenza, with no outbreaks detected; 2) Regional--outbreaks of influenza-like illness or culture-confirmed influenza in counties having a combined population of less than 50% of the state's total population; 3) Widespread--outbreaks of influenza-like illness or culture-confirmed influenza in counties having a combined population of greater than or equal to 50% of the state's total population.

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