Epidemiologic Notes and Reports Outbreak of Influenza-Like
Illness in a Tour Group -- Alaska
A 56-year-old Vermont resident began having influenza-like
symptoms on August 25, while on a cruise ship off the coast of
Alaska.
Serum specimens collected from the patient showed a fourfold rise
in
hemagglutination inhibition titer, indicating infection with a
contemporary strain of influenza A(H3N2) virus. The patient had
been
one member of a group of 35 (34 residents of Vermont, one from New
Hampshire) that had departed for Alaska on August 15 and had spent
the
period August 22-26 on a cruise ship traveling along the Alaskan
coast. Telephone interviews with all group members revealed that 19
(54%) had had a respiratory illness (fever or feverishness, and at
least two of the symptoms of cough, coryza, sore throat) between
August 23 and September 2; onset was August 25 for seven persons
(37%). The mean age of the persons who became ill was 62 years,
similar to that of the entire group. Anecdotal reports suggest high
rates of respiratory symptoms among the approximately 600 other
tourists on the vessel. Further serologic evidence for the
occurrence
of type A(H3N2) influenza infection among the tourists from Vermont
is
being sought. No other outbreaks of influenza-like illness or
confirmed influenza infections have been reported in Alaska.
Reported by: RP LaFiandra, MD, Addison County, Vermont; State
Laboratory Directors and Epidemiologists, Alaska and Vermont. Div
of
Field Svcs, Epidemiology Program Office; Influenza Br, Div of Viral
Diseases, Center for Infectious Diseases, CDC.
Editorial Note
Editorial Note: Although additional laboratory evidence of
influenza
infection is still being sought, it is likely that a cluster of
influenza A(H3N2) infections occurred in the tour group from
Vermont.
Recent reports from the World Health Organization describe the
circulation of type A(H3N2) strains in several Asian and Pacific
nations from about April to September. Considering the large
numbers
of people traveling through Alaska who are residents of, or
visitors
from, countries of Asia and the Western Pacific, importation of the
virus into Alaska in the late summer is to be expected.
The occurrence of an early outbreak of influenza A(H3N2),
coupled
with the lack of activity of type A(H3N2) virus in the United
States
last winter, suggests that this subtype will be at least partially
responsible for the influenza activity of the coming season.
Traditionally, type A(H3N2) viruses, in contrast to type A(H1N1)
viruses, have spread to older persons (as in the Alaskan outbreak)
and
have been responsible for most mortality and excess
hospitalizations,
as well as causing increases in clinic visits and absenteeism from
the
workplace or classroom. Actions to reduce this impact are detailed
in
the recommendations of the Immunization Practices Advisory
Committee
(ACIP) (1) and in the proceedings of a recent symposium (2). In
particular, these measures include vaccinating persons being
treated
for cardiopulmonary disease, residents of chronic-care
institutions,
persons over 64 years of age, and any other persons with underlying
diseases that increase their likelihood of having complications
from
viral or secondary bacterial infections. In addition, physicians,
nurses, or family members (including children) who might transmit
infections to high-risk persons should be vaccinated.
Vaccine should be routinely provided during this season for the
above high-risk persons and their close medical or family
contacts.These persons should be actively identified and informed
about the advisability of pre-winter vaccination against influenza.
Pneumococcal vaccination history should also be determined for
high-risk persons, and this vaccine should be administered
simultaneously with influenza vaccine to persons who have not
already
received it. Booster doses of pneumococcal vaccine should not be
given. For further information at the local level, contact state or
county health departments, or the American Lung Association.
References
Immunization Practices Advisory Committee. Prevention and
control
of influenza. MMWR 1987;36:373-80,385-7.
Douglas RG, ed. Proceedings of a symposium: prevention,
management, and control of influenza: a mandate for the 1980s.
Am
J Med 1987;82(suppl 6A): 1-69.
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