|
 An analysis of the genetic composition of avian viruses circulating
in North America, including the H5N2 strain, showed they do not
contain genetic markers which in the past have been linked to more
severe outbreaks in birds and transmission to humans, Alicia Fry, a
medical officer in the CDC's influenza branch, said on a conference
call with reporters.
There have been nearly 650 cases of H5N1 human infections, reported
from 15 different countries, since 2003, according to the U.S.
Department of Health and Human Services.
Two different strains have been discovered in the United States this
year. The H5N2 strain is in Arkansas, Idaho, Iowa, Kansas,
Minnesota, Missouri, Montana, North Dakota, Oregon, South Dakota,
Washington and Wisconsin. It has also been identified on farms in
Ontario, Canada. The H5N8 strain has been identified in California
and also in Idaho, U.S. Department of Agriculture data shows.
There have been no cases of the highly infectious disease in humans
since the outbreak started in the United States at the beginning of
the year. This is the most widespread bird flu outbreak in North
America in more than three decades.
In the cases involving human infection outside the United States,
illness from the H5N1 virus occurred only among people who had
direct contact with infected birds.
A principal concern with any new flu virus in birds, however, is
that it will mutate to become easily transmissible from human to
human. "At this point we don't know very much about these viruses,"
said the CDC's Fry. "They have only recently been identified."
At present, she said, "it seems the risk for human infection is very
low." But she added: "This is a rapidly evolving situation."
[to top of second column] |
Fry said the CDC will monitor any person who has been exposed to the
virus in the United States. At least 100 people have been monitored
so far.
As more people are exposed, the question of how well the virus can
be transmitted to people will become clearer.
Fry said the federal government has developed a "seed strain," a
first step toward making a vaccine. Seed strains must then be grown
and tested to ensure they will grow well in chicken eggs or cells.
Warmer weather should help lower the number of infections in birds
and curtail the virus' spread.
"As we get into spring and summer, sunshine comes and ultraviolet
light will kill influenza virus," said David Swayne, director of the
USDA's Southeast Poultry Research Lab.
Swayne was reluctant to give a time frame for an end to the
outbreak, however.
(Writing by Julie Steenhuysen and P.J. Huffstutter; editing by
Matthew Lewis)
[© 2015 Thomson Reuters. All rights
reserved.] Copyright 2015 Reuters. All rights reserved. This material may not be published,
broadcast, rewritten or redistributed.
 |
