WELLINGTON: New Zealand said Sunday that 10 students "likely" have swine flu after a school trip to Mexico, as governments across Asia began quarantining those with symptoms of the deadly virus and some issued travel warnings for Mexico.

New Zealand Health Minister Tony Ryall said none of the patients was seriously ill and they seemed to be recovering. He said they tested positive for influenza but added that there was "no guarantee" the students had swine flu.

The Israeli Health Ministry also said there is one suspected case in the country. A man who had recently visited Mexico has been hospitalised with flu symptoms while authorities try to determine whether it's actually swine flu.

At least 81 people have died from severe pneumonia caused by the flu-like illness in Mexico, according to the World Health Organization, which declared the virus a public health emergency of "pandemic potential."

The virus is usually contracted through direct contact with pigs, though some limited cases of human-to-human transmission have been reported. Health officials have sought to reassure people that it is safe to eat pork cooked thoroughly, but some governments were increasing their screening of pigs and pork imports.

The 10 students were among 13 from New Zealand's largest high school quarantined and tested for the virus after returning from Mexico. In all, 25 students and teachers arrived in the northern city of Auckland on Saturday on a flight from Los Angeles. One student had to be hospitalised, said Auckland Regional Public Health Services director Dr. Julia Peters.

"Ten students have tested positive for Influenza A, and these results will now be sent to the World Health Organization laboratory in Melbourne to ascertain whether it is the H1N1 swine influenza."

H1N1 influenza is a subset of influenza A that is a combination of bird, pig and human viruses, according to the WHO. Symptoms include a fever of more than 100 degrees Fahrenheit (37.8 degrees Celsius), body aches, coughing, a sore throat, respiratory congestion and, in some cases, vomiting and diarrhea.

At this stage other passengers on their flight were not being sought, said Health Ministry spokesman Michael Flyger.

Governments across the Asia-Pacific region and in the Middle East were stepping up surveillance for the deadly virus after Mexico closed schools, museums, libraries and theatres in a bid to contain the outbreak. About 1,000 people may have been sickened there. U.S. authorities said 11 people were infected with swine flu, and all recovered or are recovering.

At Tokyo's Narita airport — among the world's busiest with more than 96,000 passengers each day — officials installed a device at the arrival gate for flights from Mexico to measure the temperatures of passengers.

Hong Kong and Taiwan say visitors to infected areas who have fevers will be quarantined — a precaution the Philippines is also considering. The Chinese territory also joined South Korea in warning against travel to Mexico. Seoul particularly urged its citizens not to travel to the Mexican capital and three affected provinces.

Indonesia has increased surveillance at all entry points for travelers with flu-like symptoms — using devices at airports that were put in place years ago to monitor for severe acute respiratory syndrome, or SARS, and bird flu. It said it was ready to quarantine suspected victims if necessary.

China said anyone experiencing flu-like symptoms within two weeks of arriving in the country from swine-flu affected territories was required to report to authorities.

South Korea said it would bolster its quarantine measures on pork products from Mexico and the United States in the hopes of calming fears about buying and eating pork. But the country said it has no immediate plans to suspend pork imports from the North America.

Japanese Agriculture Minister Shigeru Ishiba appeared on TV to calm consumers, saying it was safe to eat pork.

In Egypt, health authorities are examining about 350,000 pigs being raised in Cairo and other provinces for swine flu. Hamed Samaha, head of the General Institute for Veterinary Health Care, urged the government to consider moving pig farms out of populated areas. Although Egypt is predominantly Muslim, about 10 percent of its population of 76 million is Christian and it has a large tourist industry.

Asia has grappled in recent years with the H5N1 bird flu virus, which has killed at least 257 people worldwide since late 2003, according to WHO. Egypt is the largest bird flu hot spot in the world outside Asia because poultry is often raised in close proximity to homes.

Scientists have warned for years about the potential for a pandemic caused by viruses that mix genetic material from humans and animals. No vaccine specifically protects against swine flu, and it is unclear how much protection current human flu vaccines might offer.