Influenza Virus Activity -- Texas, 1983-1984 Season
Analyses of reported cases of influenza, school absentee
levels,
and influenza virus isolates indicate that Texas experienced
intense
influenza activity in January and February 1984. The influenza
epidemic was more severe, when measured by number of reported
cases,
than epidemics during the 1981-1982 and 1982-1983 seasons.
Cases of influenza are reported weekly by numeric totals to the
Bureau of Epidemiology, Texas Department of Health, through a
morbidity reporting system. This system encompasses over 500
reporting sources, including physicians, city and county health
departments, and hospitals. Influenza viruses isolated in the
state
are reported through a virus surveillance system with 18
participating
laboratories. A telephone surveillance system was used to
ascertain
levels of school absenteeism and operated from January through
March
1984. Public school districts randomly chosen from an alphabetic
listing were telephoned to determine total number of schools in the
district, total enrollment at each school, and number absent at
each
school for each day of the epidemic. An absentee level of 10% or
greater for any school on any day was considered positive evidence
of
influenza activity.
A total of 102,437 influenza cases were reported in February
compared with fewer than 22,000 in February for each of the
preceding
2 years. These 102,437 reported cases are the highest number of
influenza cases reported to the Bureau of Epidemiology for any
month
since record collection began in 1920.
A total of 1,039 influenza viruses were isolated in Texas from
November 1, 1983, through April 30, 1984. Seventy-two percent of
these were isolated from specimens collected from January 22
through
February 18 (weeks 4-7 of the epidemic). Influenza type A(H1N1)
virus
represented 50% of all influenza viruses reported. Influenza B and
influenza A(H3N2) comprised 48% and 2%, respectively. In March,
82%
of the influenza viruses reported were type B.
Two hundred forty-two districts, representing 903 schools in
209
counties, were contacted between January 2 and March 30. Over 40%
of
the 315 schools surveyed during January 22-February 18 experienced
absentee levels greater than 10%; 9% had absentee levels greater
than
20%. During January 29-February 4, 70% of the 79 schools surveyed
had
absentee levels above 10%. No districts contacted after March 11
reported a school with an absentee level of 10% or greater.
Reported by WP Glezen, MD, Influenza Research Center, Baylor
College
of Medicine, Houston, JP Taylor, MPH, JN Perdue, Bureau of
Epidemiology, CE Alexander, MD, State Epidemiologist, Texas Dept of
Health.
Editorial Note
Editorial Note: This information from Texas documents the
unusually
high rate of influenza morbidity in association with widespread
increases in school absenteeism in January and February and
highlights
at the state level the trends seen regionally and nationally during
the past influenza season (1).
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