19 February 2004
U.S. Version of Bird Flu Not Widespread, Testing Reveals
Officials say U.S. strain not hazardous to human health
By Charlene Porter
Washington File Staff Writer
Washington -- Bird flu has appeared in poultry flocks in two U.S.
states -- Delaware and Pennsylvania -- but testing of neighboring
flocks reveals no widespread infection so far. Agriculture officials
emphasize that the strains affecting U.S. flocks are not the same
as that discovered in Asia where an estimated 80 million birds
have been culled to contain avian influenza and prevent a human
"The AI (avian influenza) strain in affected states is not
the same strain of the virus that is affecting birds and some people
in Asia," said Bobby Accord, administrator of the U.S. Animal
and Plant Health Inspection Service (APHIS). "The Asia strain
is highly pathogenic avian influenza (HPAI) and the United States
has not had an incidence of HPAI for 20 years."
In Delaware, testing of birds is still under way and two flocks
have been culled after discovery of the virus. Testing will extend
into farming operations in areas of Virginia and Maryland nearby
the Delaware flocks, though no infected birds have been found in
those neighboring states. In Pennsylvania, the virus was detected
in routine surveillance and had not emerged as illness in the birds.
No birds have been culled in Pennsylvania, according to the latest
APHIS status report.
A few infected birds were detected in a New Jersey market, but
no virus has been detected in poultry flocks in that state, which
shares borders with both Pennsylvania and Delaware.
"Low Pathogenic Avian Influenza viruses are endemic in wild
waterfowl and migrating bird populations worldwide," said
Accord. "Consequently, each year we occasionally find some
occurrences of low pathogenic avian influenza in domestic poultry." Accord
acknowledged that the widespread occurrence of the dangerous H5N1
in Asia has focused heightened attention on the appearance of the
U.S. cases, but it emphasized that the low pathogenic forms of
bird flu do not pose a risk to human health.
According to the U.S. Department of Agriculture, more than 20
nations have suspended imports of chicken from the United States
because of the occurrence of bird flu. However, most nations have
limited their prohibitions to meat produced in those areas where
the virus has been confirmed.
With this agriculture investigation pending in the United States,
the U.S. Centers for Disease Control and Prevention issued new
guidelines on procedures to be used in culling flocks to prevent
the further spread of the virus and to protect the workers doing
the culling. This advice is of especially keen importance in Asia,
however. The reason international health officials are so watchful
of the outbreaks in eight Asian nations is because they fear that
the H5N1 strain could enter the bloodstream of a human -- perhaps
a worker involved in destroying infected flocks. Then a determined
virus might be able to use that human bloodstream as its own laboratory,
mutating itself into another form of the virus that would be more
easily transmitted person-to-person, thus creating conditions for
a widespread human epidemic.
As of February 19, the World Health Organization (WHO) had confirmed
31 cases of bird flu occurring in humans in Asia, and all seem
to have resulted from a person's direct contact with a diseased
bird or its fecal matter. Twenty-two of those cases have been fatal,
an alarming mortality rate attributed to the fact that H5N1 has
only rarely leapt from birds to humans before, and human beings
have developed no immunity to this strain.
The emergence of human cases is slow, however, and that's good
news, health officials say. Considering that H5N1 has been circulating
among Asian birds for months, the fact that only 31 cases have
been confirmed in humans indicates that the virus doesn't make
the leap from birds to humans with ease. On the other hand, a WHO
status report on the outbreak February 12 indicated that experts
probably don't know all there is to know about the human cases,
and raises the possibility that many human cases occurring on remote
farms in Asia have not been reported.