Reports of influenza virus isolates received weekly at CDC from
collaborating laboratories peaked in February and are now declining
in
parallel with morbidity indices of influenza (Figure 1) (1). A
preliminary total of 1,317 influenza virus isolates has been
reported
this season through March 23, 1984; 807 (61%) were identified as
type
A(H1N1); 452 (34%) as type B; and 58 (4%) as type A(H3N2). One or
more types of influenza virus have now been isolated in 49 states
and
the District of Columbia.
Although outbreaks in nursing homes have been uncommon this
season, as most activity has been of type A(H1N1) virus among
children
or young adults, a few have been documented in association with
types
A(H3N2) or B infection. Five such outbreaks have been
reported--three
from California and one each from Massachusetts and Minnesota. The
first began at a nursing home in San Bernadino at the end of
December
1983, when 15 (31%) of 48 residents developed influenza-like
illness.
Serologic testing has shown diagnostic rises in titers to influenza
type A(H3N2) in three of four patients. In late February, another
influenza outbreak was noted in a Los Angeles hospital for elderly
patients. Influenza-like illness affected 30 (38%) of the 80
patients, and one type B isolate was obtained. Further serologic
studies also indicated type B infections. A small outbreak was
reported early in March in San Francisco, where all 10 patients in
one
ward of a nursing hospital for the elderly developed influenza-like
illnesses, and four type B isolates were identified. In
Massachusetts, two type A(H3N2) virus isolates were obtained in
March
from an outbreak of influenza-like illness in a nursing home. In
Minnesota, an outbreak of type B that began in mid-March was
recently
documented from a Hennepin County nursing home. Influenza-like
illness affected 29 (23%) of the 200 residents, and type B was
identified in four of six specimens collected.
Reported by A Taylor, MPH, T Stephenson, MPH, San Bernadino County
Health Dept, F Sorvillo, MPH, Los Angeles County Health Dept, B
Louie,
S Dritz, MD, San Francisco County Health Dept, J Schieble, PhD, R
Murray, DrPH, California Dept of Health Svcs; J McDonough, Hennepin
County, D Peterson, MPH, Minnesota Dept of Health; J DeCinti, MEd,
Massachusetts Dept of Public Health; State Epidemiologists and
Laboratory Directors; Statistical Svcs Br, Div of Surveillance and
Epidemiologic Studies, Epidemiology Program Office, Systems
Development Br, Computer Systems Office, Statistical Svcs Activity,
Influenza Br, Div of Viral Diseases, Center for Infectious
Diseases,
CDC.
Reference
CDC. Influenza Activity--Mississippi, United States,
Worldwide.
MMWR 1984:33;131-40.
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