There are no pigs in the Chinese mainland infected with the H5N1
virus, or avian flu virus, and relevant research has reached no
clear conclusion on H5N1 infecting pigs, announced the Ministry of
Agriculture on Thursday.
In an experiment on isolation and identification of H5N1 and
H9N2 of sub-type influenza virus in pigs, two strains of H5N1 were
isolated from samples collected between 2001 and 2003, said Jia
Youling, director of the Veterinary Bureau of the ministry, at a
press conference.
Upon receiving the results, the ministry began the verification
process immediately, which showed that the research isolates were
highly isogenous with the H5N1 duck virus isolated before. However,
no new strains were isolated during the intense surveillance and
study efforts, which suggested that it was an "incidental
infection" by the duck-origin avian influenza (AI) virus, said Jia,
also national chief veterinary officer.
He noted that the ministry has kept sharp vigilance over any
possibility of AI cross-species transmission and the infection of
mammals. Since 1999, the ministry has called on institutes to carry
out research activities on AI's possible invasion of mammals. In
addition, the epidemiological study was launched nationwide.
After the outbreak of avian flu in some places in China this
year, the ministry required local agencies to tighten up
surveillance efforts on pigs when mapping out the AI monitoring
arrangements.
At the same time, the ministry required relevant institutes to
continue and to intensify the research on the rules of genetic
evolution of AI isolates as well as possible mammal infection
mechanisms. The National AI Reference Lab, National Epizootics
Research Center and Veterinary Diagnostic Center of the ministry
were arranged to launch targeted surveillance and study of the
possible carriage of AI virus by pigs.
"The surveillance results show that no other H5N1 strain was
isolated from pigs in the mainland," said Jia.
"But that carrying a virus does not mean infection. Similarly,
the virus identified does not necessarily mean that there is a
presence of an epidemic."
"Once the epidemic breaks out, we will provide timely
notification in accordance with the rules of international
organizations," he said.
In addition, due to the very limited strains isolated, no clear
conclusion could be made on pig-to-human infection of H5N1. "But no
matter whether there is a conclusion or not, we will certainly
reinforce research programs on the relationship between H5N1
carried by pigs and avian flu infecting human beings. And by doing
so, we will be able to prevent and control any outbreak?of
this kind," Jia noted.
According to the ministry, studies from the international
community indicate that the flu virus can infect not only poultry,
but also mammals. There were reports of some mammals' carriage of
AI virus in Asia, such as cat, tiger, cloud leopard and pig.
In 1918, the first swine flu case was reported in America. In
1931, the first H1N1 virus was isolated, followed by the H3, H4 and
H9 sub-types from countries in Europe, Asia and North America.
(Xinhua News Agency August 27, 2004)