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