Containing the Hong Kong Poultry Flu
To test its effect, veterinarian David Swayne will inoculate chickens with
virus extracted from this breeder stock vial.
On May 21, 1997, a 3-year-old boy in Hong Kong died of medical complications
from a flu virus, and suddenly the world held its breath.
Hong Kong and other locations in China have a history of being the starting
zones for world influenza pandemics--worldwide epidemics bringing illness and
death to millions of people. In 1957, and again in 1968, new flu pandemics
arose from this part of Asia. Would Hong Kong be the beginning of another one
like the Spanish flu, the worst influenza of the 20th century, which killed 30
million people from 1918 to 1919?
What happened in the months that followed the young boy's death is a story
of quick thinking and teamwork between private and public research agencies,
including USDA's Agricultural Research
Service. This time, no pandemic occurred. But scientists got an important
drill in prevention, and the world got a wake-up call.
Hong Kong, May 21: The 3-year old
victim's physician sends samples of respiratory secretions from the child to
the Hong Kong Department of Health. In a laboratory there, an unusual influenza
virus is obtained from this clinical sample. Department of Health officials
forward this virus to the Centers for Disease Control and Prevention (CDC) in
Atlanta, Georgia, and to counterpart laboratories at the National Institute for
Medical Research in London, England, and the National Influenza Center at
Rotterdam, The Netherlands.
Atlanta, August 1: At the CDC,
microbiologist Nancy Cox faces two big tasks--a scientific one and a practical
one. She has just learned that the European labs, working independently,
reached the same conclusion as the CDC: The mystery virus is H5N1, short for
hemagglutinin subtype 5 and neuraminidase subtype 1, both proteins on the virus
But H5N1 is a bird virus. Has it changed hosts? More important, can the
infection pass from birds to humans? Or, even worse, has the virus developed a
deadly new trick: the ability to pass from person to person? This is how
One way to answer the scientific questions, Cox knows, is to compare viral
genes from the boy's sample with virus from an infected chicken. But handling
such viruses requires a special lab--a biosafety level-3 (BSL-3)--designed to
contain deadly viruses. CDC Influenza Branch does not have a BSL-3 laboratory
available for use: Human influenza viruses are handled in a lower level of
Veterinary medical officers David Suarez (left) and David Swayne evaluate
tissue sections (top monitor) from chickens infected with Hong Kong H5N1
influenza. The bottom monitor displays a photo of chicken legs showing physical
damage resulting from the flu virus.
Atlanta, August 25: Cox reaches
for the phone and dials David E. Swayne. In Athens, about an hour east of
Atlanta, Swayne, a veterinarian, heads the ARS Southeast Poultry Research
Laboratory (SEPRL). He leads a team of experts studying poultry influenza
viruses, including the H5 subtype. In 1994 and 1995, the Athens researchers
helped understand an outbreak in Mexico of H5N2, a poultry virus strain not
seen in humans.
Swayne and colleague Mike Perdue, a microbiologist, have been working with
several companies to come up with poultry vaccines for H5-type viruses. Their
laboratory has both a BSL-3 facility and sophisticated means of detecting and
identifying these viruses. This gives them the ability to work without
endangering humans or poultry in the surrounding community.
Swayne agrees to help, recognizing the importance of H5N1 not only to
humans, but to the U.S. poultry industry. He offers Cox's group his
biocontainment facility until a CDC facility can be made available.
"The offer was immediately accepted by the CDC," says Cox.
"Having the facility was essential to analyzing the first virus from the
The CDC experts begin an ongoing collaboration with an ARS team that
includes Swayne, Perdue, veterinarian David Suarez, and microbiologist Stacey
Athens, end of August to early September:
At the CDC's recommendation, everyone on the project begins taking
rimantadine, an antiviral drug. In the containment rooms, scientists wear
special masks covering nose and mouth. Later, CDC, ARS, and USDA's Animal and
Plant Health Inspection Service (APHIS) upgrade their protection while working
with infected poultry to include wearing air-filtering hoods that cover the
head and protect the eyes.
Suarez and Perdue sequence the genetic material of the chicken viruses from
Hong Kong and, with CDC, compare this information to the H5N1 viruses from
people. This shows that the human viruses were from
Swayne discovers that the human virus kills test poultry in less than 48
hours. The virus replicates in vascular endothelial cells--those that line
blood vessels throughout the body--and in muscle cells of the heart. The H5N1
virus from chickens attacks poultry the same way as this human-source virus.
Schultz-Cherry shows a host protein that may be a factor in the disease.
Hong Kong, December 2: In a fax
to Swayne, Les Sims, with Hong Kong's Agriculture and Fisheries Department,
requests test materials for H5N1. At the time, Sims' staff is using deadly Hong
Kong H5N1 virus to make diagnostic proteins, or antigens, used to detect
antibodies in blood of infected birds.
While a "hot" virus makes an effective antigen, using a related,
mild strain that doesn't strike humans would be safer. Swayne dispatches a
courier with safer diagnostic materials from his lab to help Sims protect his
employees and speed detection.
Swayne also gets a call from Charlie Beard, retired SEPL director and now
vice president for research and technology for the U.S. Poultry and Egg
Association, a key poultry industry trade group. Beard is concerned about
protecting U.S. poultry from H5N1. Swayne briefs him on the latest findings
from CDC and ARS.
Hong Kong, December 5: H5N1
claims the life of a 54-year-old man in Hong Kong.
Athens, December 17: Swayne begins a new
test of H5N1's virulence. Using virus isolated from a blood sample of the
latest victim, he infects a poultry flock of about 20 birds in the Athens
biocontainment facility. Within 24 hours, the entire flock is dead.
"It wasn't the fact that they died that struck me," he recalls.
"It was how quickly it happened."
This finding heightens a previously raised question: Should there be an
emergency protocol for vaccinating U.S. poultry? Swayne, Perdue, and Suarez
decide to test three vaccines developed for other H5 poultry influenza viruses.
All are 90 to 100 percent effective if the right dosage and protocols are used.
In a majority of the 20-bird test flocks, the virus that could kill in 24 hours
is now defeated.
Hong Kong, December 29: While vaccine
may have been found, Hong Kong officials aren't taking chances. They begin a
mass slaughter of 1.5 million chickens and an industrywide cleanup of poultry
Athens, December 30: Beard calls Swayne,
concerned about whether a protocol for poultry vaccination should be developed,
considering how lethal H5N1 is to birds. Swayne reassures him one is under way.
This is important, as accidental infections could endanger the world's valuable
poultry breeding stock and ultimately contribute to shortages of poultry meat
Washington, D.C., January 8, 1998:
Swayne and Beard meet with APHIS leaders, who decide to approve the
industry's stockpiling of H5 vaccines, in the event the virus spreads outside
of Hong Kong. APHIS drafts an emergency vaccination plan.
Washington, D.C. January 18: A joint
CDC-ARS article appears in Science describing the characteristics of the
first human H5N1 virus from Hong Kong.
Hong Kong, late March: No new
cases of H5N1 have been reported for some time. Swayne and Perdue fly to Hong
Kong with new poultry vaccines they co-developed with several cooperators. They
provide Les Sims samples, so he can test them at the Hong Kong Agriculture and
Fisheries Department. Perdue visits zoo officials and helps test the vaccine in
some exotic birds.
Washington, D.C., August, 1998: A joint ARS-CDC article appears in
the Journal of Virology fully describing the first human and poultry
At Present:Though the origin of H5N1 is still unknown, the massive
worldwide media coverage has died down as the outbreak has subsided. The virus
fades into "old news."
The Hong Kong government, initially criticized for destroying all its
poultry to eradicate potential virus carriers, is now credited with preventing
a more serious outbreak.
Research teams worldwide, including those led by Sims, Cox, and Swayne,
continue to study H5N1 to find out what enabled it to change hosts. If they can
discover why this happened, they may be able to stop similar outbreaks
sooner.--By Jill Lee,
Agricultural Research Service Information Staff.
David E. Swayne, USDA-ARS
Southeast Poultry Research Laboratory, 934 College Station Rd., Athens, GA
30605; phone (706) 546-3433, fax (706) 546-3161.
"Containing the Hong Kong Poultry Flu Outbreak" was
published in the December 1998 issue
of Agricultural Research magazine.