Influenza Update -- United States SWINE INFLUENZA-LIKE ISOLATE --
NEVADA
An influenza isolate submitted to CDC from Nevada for reference
analysis has been identified as a swine influenza-like virus,
antigenically similar to A/New Jersey/76.* This continues a pattern
of
occasional human infections with swine influenza viruses currently
circulating in pigs.
The virus was isolated from a 4-year-old girl who was
hospitalized
in Las Vegas on February 6 with a temperature of 104 F (40 C),
cough,
left lower lobe pneumonia, and pancytopenia. The child had been
diagnosed in December 1981 as having acute lymphocytic leukemia,
for
which chemotherapy had been administered continuously since that
time. When she visited Los Angeles for intravenous chemotherapy in
an
outpatient department on January 29, 1982, her leukemia was
considered
to be in remission, and she had a clear chest on physical
examination
and no symptoms of respiratory infection. Between January 30, the
date of her return to Las Vegas, and February 6, the child visited
only 2 homes, occupied by close family members and their friends,
in
residential subdivisions in Las Vegas. She was in contact with 14
persons including 9 children or young adults. Thirteen of the
contacts were interviewed recently, and none reported either
respiratory illness at the time of the child's influenza illness or
reported contact with pigs. None of these contacts had serum
hemagglutination-inhibition titers of
10 to swine influenza-like
viruses that could not be explained by the individual's age or
probable receipt of swine influenza vaccine during military service
in
1976-1977. There were no community morbidity indices indicating
influenza outbreaks in Las Vegas from January through April, but 2
influenza A(H1N1) (closely related to A/England/333/80) and 18
influenza B viruses were isolated in 2 hospitals performing virus
diagnosis.
After the child was hospitalized on February 6, her pneumonia
progressed despite therapy with broad-spectrum antibiotics. On
February 11 she was transferred to a Los Angeles hospital where she
died on February 14. Laboratory tests in Nevada and Los Angeles
were
negative for any infectious agent except influenza virus.
Interviews
at the hospitals in Las Vegas and Los Angeles have not identified
any
unusual respiratory illnesses among patients or staff in contact
with
the child. Antibody prevalence to swine influenza-like virus in
young
children in Las Vegas and Los Angeles, as well as contacts of the
patients in the Los Angeles hospital, will be studied. No other
human
isolations of swine influenza-like viruses have been reported to
CDC
this winter.
Reported by O Ravenholt, MD, Clark County Health District, J
McCusker,
MD, RR Belliveau, MD, Southern Nevada Memorial Hospital, P
Reichelderfer, PhD, Sunrise Hospital, BA Neyland, MD, Las Vegas, JH
Carr, MD, State Epidemiologist, Nevada State Dept of Human
Resources;
J Cherry, MD, UCLA, B Agee, MD, Los Angeles County Health Dept, R
Roberto, MD, J Chin, MD, State Epidemiologist, California Dept of
Health Svcs; Field Svcs Div, Epidemiology Program Office, Influenza
Br, Div of Viral Diseases, Center for Infectious Diseases, CDC.
Editorial Note
Editorial Note: This incident is consistent with the infection in
1974 by swine influenza-like virus of an immunocompromised child,
who
subsequently died (2). Sporadic isolations of swine influenza-like
virus from children or young adults were reported in 1976-1977 (3)
and
also in 1978-1979 and 1979-1980 (4). The sporadic isolations after
1974 were not associated with unusual clinical symptoms, and the
source of these infections, as well as the case in 1974, could be
attributed to exposure to swine. Serologic evidence of swine
influenza infection involving some members of a farming family
exposed
to pigs has also been reported (5). The single proven outbreak of
swine influenza among humans in 1976, at Fort Dix, New Jersey, is
believed to have involved person-to-person transmission over a few
weeks in the atypical environment of the training camp (6).
Low-level
person-to-person transmission may also have been responsible for 3
reported serologically diagnosed cases of swine influenza in
1975-1977, when, as in the case of the Las Vegas child, no exposure
to
swine could be identified (3,7).
The lack of other swine influenza-like virus isolations from
humans in Nevada or California this winter, despite the isolation
of
numerous influenza B and human strains of influenza A(H1N1) viruses
in
these states this winter, and the lack of respiratory illness among
any of the child's family contacts (many of them apparently
susceptible as judged by their antibody status and age) support the
conclusion that swine influenza-like viruses that currently
circulate
in pigs have not demonstrated the propensity to cause human
epidemics. Nevertheless, transmissions from swine to human, and
subsequently from person to person at generally low levels will
probably continue to be detected occasionally by virus surveillance
activities.
References
CDC. Influenza nomenclature. MMWR 1980;29:514-5.
Smith, TF, Burgert, EO, Dowdle, WR, Noble, GR, Campbell, RF,
Van
Scoy, RE. Isolation of swine influenza virus from autopsy lung
tissue of man. N Engl J Med 1976;294:708-10.
CDC. Influenza Surveillance Report No. 92, January 1981, pp
36-7.
CDC. Influenza Surveillance Report No. 93, in press.
O'Brien RJ, Noble GR, Easterday BC, Kendal AP, Shasby DM,
Nelson
DB, Hattwick MAW, Dowdle WR. Swine-like influenza virus
infection
in a Wisconsin farm family. J Infect Dis 1977;136
(Suppl.):S390-6.
Top FH Jr, Russell PK. Swine Influenza A at Fort Dix, New
Jersey
(January- February 1976). IV. Summary and speculation. J
Infect
Dis 1977;136 (Suppl.):S376-80.
Thompson RL, Sande MA, Wenzel RP, Hoke CH, Gwaltney JM.
Swine-influenza infection in civilians. N Engl J Med
1976;295:714-5.
*Redesignated as H1N1 subtype following a revision of influenza
nomenclature (1).
Disclaimer
All MMWR HTML documents published before January 1993 are electronic conversions from ASCII text into HTML. This conversion may have resulted in character translation or format errors in the HTML version. Users should not rely on this HTML document, but are referred to the original MMWR paper copy for the official text, figures, and tables. An original paper copy of this issue can be obtained from the Superintendent of Documents, U.S. Government Printing Office (GPO), Washington, DC 20402-9371; telephone: (202) 512-1800. Contact GPO for current prices.
**Questions or messages regarding errors in formatting should be addressed to mmwrq@cdc.gov.
