Current Trends
Update: Influenza Activity -- United States, 1994-95 Season
In collaboration with the World Health Organization (WHO)
international collaborating laboratories and state and local health
departments in the United States, CDC conducts surveillance to
monitor influenza activity and to determine the antigenic
characteristics of circulating strains of influenza viruses. This
report describes influenza viruses isolated from sporadic cases of
influenza in the United States during July-September 1994 and
summarizes influenza surveillance findings from October through
mid-November 1994.
From July through September, influenza type A(H3N2) viruses
were isolated from sporadic cases in California, Hawaii, Michigan,
New York, and South Dakota; influenza type A(H1N1) was reported
from Nevada and influenza type B from Texas. All of these isolates
were characterized at CDC and are antigenically similar to the
A/Shangdong/09/93-like (H3N2), A/Texas/36/91-like (H1N1), and
B/Panama/45/90-like influenza virus strains included in the 1994-95
influenza vaccine.
From October 2, when WHO international collaborating
laboratories in the United States began seasonal influenza virus
surveillance, through November 19, two of 2693 specimens tested for
respiratory viruses yielded influenza virus. Influenza type A was
identified by antigen detection from nasopharyngeal swab specimens
collected November 2 from a patient in New Mexico and November 3
from a patient in New York. Reports from state and territorial
epidemiologists and from sentinel physicians have indicated low
levels of influenza-like illness nationwide.
Reported by: Participating state and territorial epidemiologists
and state public health laboratory directors. World Health
Organization collaborating laboratories. Sentinel Physicians
Influenza Surveillance System of the American Academy of Family
Physicians. WHO Collaborating Center for Surveillance,
Epidemiology, and Control of Influenza, Div of Viral and
Rickettsial Diseases, National Center for Infectious Diseases, CDC.
Editorial Note
Editorial Note: Although the time of onset of influenza epidemics
can vary substantially by year, the pattern from October through
mid-November 1994 was typical for influenza activity in the United
States. In some recent influenza seasons (e.g., 1991-92 and 1993-
94) (1,2), influenza activity began earlier than usual; however,
regional activity usually does not begin until December, and
influenza activity usually peaks during January or February.
Accordingly, the Advisory Committee on Immunization Practices
recommends that the optimal time for organized vaccination
campaigns for persons in high-risk groups is usually from
mid-October through mid-November. Vaccine should be offered to
high-risk persons up to and even after influenza activity is
documented in a community (3); following vaccination, 1-2 weeks are
required for the development of protective antibody titers. When
influenza vaccine is administered after influenza type A outbreaks
have begun in a community, the antiviral drugs amantadine and
rimantadine can be administered to protect against influenza until
vaccine-induced antibody has developed. These drugs are not
effective against influenza type B. Updated recommendations for the
use of these drugs will be published in MMWR during December 1994.
Worldwide virologic surveillance is conducted throughout the
year to monitor antigenic changes in the circulating influenza
virus strains. Through this system, antigenic changes in influenza
virus strains have been detected sufficiently early to formulate
influenza vaccines that frequently have contained strains similar
to those that subsequently have circulated in the United States at
epidemic levels. Although influenza activity is difficult to
predict, it is expected that during the 1994-95 season in the
United States, both type A and type B viruses will circulate.
Information about national influenza surveillance is updated
weekly from October through May and is available through the CDC
Voice Information System, telephone (404) 332-4555. Information
about local influenza activity is available from county and state
health departments.
References
CDC. Influenza -- United States, 1989-90 and 1990-91 seasons.
MMWR
1992;41(no. SS-3):35-46.
CDC. Update: influenza activity -- United States and worldwide,
1993-94 season, and composition of the 1994-95 influenza vaccine.
MMWR 1994;43:179-83.
ACIP. Prevention and control of influenza: part I, vaccines --
recommendations of the Advisory Committee on Immunization Practices
(ACIP). MMWR 1994;43(no. RR-9).
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| Erratum: Vol. 43, No. 46
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| SOURCE: MMWR 43(51);961 DATE: Jan 06, 1995
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| In the article "Update: Influenza Activity -- United States,
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| 1994-95 Season," an error appeared on page 848. In the first
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| sentence of the second paragraph, Minnesota, not Michigan, should
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| have been listed among the states that reported sporadic isolates
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| of influenza type A(H3N2) during July-September 1994.
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