28 January 2004
CDC Issues Fact Sheet on Asian Avian Flu Strain
CDC works with international health officials
to evaluate outbreak
The U.S. Centers for Disease Control and Prevention is working
with international health officials to evaluate the outbreak of
avian flu occurring in Asia, resulting in some human deaths. Millions
of poultry have been killed in order to contain the disease.
CDC issued a fact sheet on the disease January 27.
The following term is used in the fact sheet:
H5N1: This is the designation for the strain of influenza virus
that is being transmitted from birds to humans. The letters "H" and "N" stand
for haemagglutinin and neurominidase, two proteins found in the
molecule of the influenza virus. These proteins combine in different
ways as the cells mutate, creating different strains of the disease
with variable properties. Health officials believe there is evidence
that the H5N1 has a unique capacity to jump the species barrier
and cause serious and sometimes fatal disease in humans.
Following is the CDC fact sheet:
U.S. Centers for Disease Control and Prevention
January 27, 2004
Influenza A(H5N1) Outbreak
Recent Influenza A(H5N1) Cases
The Government of Vietnam has reported hospitalized cases of severe
respiratory illness in people from provinces surrounding Hanoi
beginning in October 2003. Avian influenza A(H5N1) virus infections
have been confirmed in some of these patients. Deaths have been
Visit http://www.who.int/en/ for updated case counts.
Influenza A(H5N1) viruses normally circulate among wild birds
but can infect poultry and rarely have infected people in the past.
In 1997, 18 persons in Hong Kong were hospitalized because of influenza
A(H5N1) infections and six of them died. In 2003, two residents
of Hong Kong who traveled to China developed influenza A(H5N1)
virus infections and one of them died. In Vietnam, large outbreaks
of influenza A(H5N1) have been reported among poultry in the southern
and northern regions of the country. The World Health Organization
(WHO) has reported that the H5N1 strain implicated in the outbreak
has been sequenced. All genes are of avian origin, indicating that
the virus has not acquired human genes. The acquisition of human
genes increases the likelihood that a virus of avian origin can
be readily transmitted from one human to another.
On January 23, 2004, WHO reported two laboratory-confirmed cases
of H5N1 avian influenza in children in central Thailand. The first
case is in a 7-year-old boy from Suphanburi province who developed
fever and cough on January 3; his illness progressed to acute respiratory
distress syndrome on January 13. The second case is a 6-year-old
boy from Kanchanaburi province who developed fever on January 6,
followed a week later by severe pneumonia with acute respiratory
distress syndrome. As of January 25, 2004, both patients were alive.
More information on this report is available at http://www.who.int/en/.
H5N1 Outbreak Investigation
WHO is coordinating an investigation in Vietnam. Staff from CDC
have traveled to Vietnam to work with WHO and Vietnam's human and
animal health authorities to evaluate the situation, including
patterns of transmission of the influenza A(H5N1) viruses. The
investigation will focus on determining specific characteristics
of influenza A(H5N1) viruses isolated from human cases and poultry
and on determining how people became infected. In addition, increased
surveillance will help investigators determine how many people
in Vietnam already have been infected with the influenza A(H5N1)
virus and whether other people are continuing to be infected. WHO
will be collaborating closely with health authorities in Thailand
in responding to the situation there.
H5N1 Infections Among Poultry in Asia
Outbreaks of avian influenza A(H5N1) have been reported among
poultry in Vietnam, South Korea, Thailand, Japan, Indonesia, Myanmar,
Cambodia, and China. H5N1 has been confirmed in smuggled birds
in Taiwan, but not in wild flocks or poultry. Additionally, there
have been reports of poultry deaths in Laos and Pakistan. Influenza
A(H5N1) Outbreak (continued from previous page)
U.S. residents who are traveling outside the United States should
consult their physician for advice about which vaccines they should
obtain. In Vietnam and in other tropical regions, influenza can
occur at any time during the year. Thus, persons who are at increased
risk of developing influenza-related complications and healthy
persons who wish to decrease their risk of becoming ill with influenza
should receive the 2003-04 trivalent influenza vaccine. The vaccine
will protect against three viruses and offers some protection against
variants of them as well.
At this time CDC and WHO have not issued any travel alerts or
advisories for the region in response to the H5N1 outbreak. However,
travelers to countries in Asia with documented H5N1 outbreaks are
advised to avoid poultry farms, contact with animals in live food
markets and any surfaces that appear to be contaminated with feces
from poultry or other animals. For more information about topics
related to travelers' health, visit http://www.cdc.gov/travel/.
Enhanced U.S. Influenza Surveillance At this time, CDC recommends
enhanced surveillance efforts by state and local health departments,
hospitals, and clinicians to identify patients who have been hospitalized
with unexplained pneumonia, ARDS, or severe respiratory illness
AND who have traveled to countries in Asia with documented H5N1
outbreak. CDC will make additional recommendations on enhanced
surveillance if influenza A(H5N1) activity continues to evolve.
More Information About Influenza For further details about the
reported cases of influenza A(H5N1) in Vietnam, see the WHO Web
site http://www.who.int/en/. Additional information about influenza
is available on the CDC Web site at http://www.cdc.gov.