Influenza update: Influenza activity continues to decline in
the
United States, as judged by reductions in the proportion of states
reporting outbreaks of influenza-like illness (Figure 3), the
number
of patients with influenza-like illness reported by family
physicians
(Figure 4), and laboratory reports of influenza virus isolations
(1).
In recent weeks, influenza type B has been more frequently
identified
than type A(H1N1), which had previously predominated.
Antigenic analysis of influenza type B viruses: Influenza type
B,
which has caused outbreaks in some countries in the Northern
Hemisphere this winter, including the United States, has generally
been poorly inhibited by animal sera to the B/Singapore/222/79
reference strain in hemagglutination-inhibition (HI) tests. A
spectrum of different reaction patterns has been observed with
recent
isolates (Table 4). Most isolates from the United States cannot be
distinguished in HI tests from B/USSR/100/83 and B/Norway/1/84,
although a few variants like B/Texas/1/84 are distinct.
Reported by State and Territorial Laboratory Directors and
Epidemiologists; Other Collaborating Laboratories; Physician
Reporters
of the American Academy of Family Physicians; Statistical Svcs Br,
Div
of Surveillance and Epidemiologic Studies, Epidemiology Program
Office, Computer Systems Office, Statistical Svcs Activity,
Influenza
Br, Div of Viral Diseases, Center for Infectious Diseases, CDC.
Reference
CDC. Update: influenza activity--United States. MMWR
1984;33:166-7.
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