Meat from pigs infected with the new H1N1 virus shouldn't be used for human consumption, the World Health Organization cautioned on Wednesday, adding it was drawing up guidelines to protect workers handling pigs.
The WHO comments appear more cautious than those from the Food and Agriculture Organization (FAO) and World Organization for Animal Health (OIE), which said import bans are not required to safeguard public health because the disease is not food-borne and has not been identified in dead animal tissue.
That said, the WHO is not discouraging people from eating pork.
It said on Thursday that pork was safe to eat and that existing sanitary and animal health checks were sufficient to safeguard the food supply against the H1N1 virus.
"Eating pork is not a danger in terms of getting this infection," Keiji Fukuda, acting WHO assistant director-general, told a news conference in Geneva.
As many as 20 governments have restricted pork imports from Mexico and other flu-affected countries in response to fears about the new strain, which scientists say is a mixture of swine, avian and human flus.
The WHO however said it was possible for flu viruses to survive the freezing process and be present in thawed meat, as well as in blood.
"Meat from sick pigs or pigs found dead should not be processed or used for human consumption under any circumstances," Jorgen Schlundt, director of WHO's Department of Food Safety, Zoonoses and Foodborne Diseases.
"While it is possible for influenza viruses to survive the freezing process and be present on thawed meat, there are no data available on the survival of Influenza A/H1N1 on meat nor any data on the infectious dose for people," he wrote in an email reply to questions from Reuters concerning the safety of pork, respiratory secretions and blood of H1N1-infected pigs.
Schlundt warned people to be cautious with blood and meat-juices from H1N1-infected pigs.
"The likelihood of influenza viruses to be in the blood of an infected animal depends on the specific virus. Blood (and meat-juice) from influenza H1N1-infected pigs may potentially contain virus, but at present, this has not been established," Schlundt said.
"Nonetheless, in general, we recommend that persons involved in activities where they could come in contact with large amounts of blood and secretions, such as those slaughtering/eviscerating pigs, wear appropriate protective equipment," he said.
The new H1N1 swine flu virus is being transmitted from person to person, not from pigs to people.
Its global spread has prompted many countries to limit pork imports, however. As many as 20 governments have imposed import bans on live pigs and meat from affected countries to prevent exposure to the virus. Such fears increased after Canadian authorities said on Saturday a herd of swine was infected by a farmer who had returned from Mexico.
The WHO said 22 countries have officially reported 1,534 cases of the flu virus.
While health officials say the outbreak appears to be slowing down in Mexico, authorities everywhere are asking how far the virus would spread and how serious it would be.
U.S. officials confirmed that a Texas woman with the H1N1 swine flu virus died earlier this week, the second death outside Mexico. Last week, a Mexican toddler visiting Texas died. Mexican officials have reported 29 confirmed deaths.
While the new virus is mainly spread from person to person through coughing and sneezing, experts do not know for sure how this virus came to be, which animal passed it to the first human patient and when that occurred.
But the case of the farmer infecting the pigs in Canada fueled fears of the virus yet again jumping the species barrier - this time from pig to human - and possibly becoming more virulent in the process.
Joseph Domenech, FAO chief veterinary officer, said on Tuesday: "This new strain of influenza virus does not contaminate humans easily and has a very low pathogenicity for both humans and pigs, unlike the avian flu which killed millions of poultry."
On Tuesday, Alex Thiermann, senior adviser to the OIE's director-general, said there was no difference between raw and cooked meat in terms of H1N1 transmission risks.
"The OIE is very concerned that differences are being made between cooked and not cooked meat. All pork products are safe for consumption," Thiermann said.