Global airlines, still reeling from the H1N1 flu-virus scare, have stepped up efforts to protect passengers from health risks on international flights.

In Asia, carriers spooked by the memory of SARS have stepped up cabin cleaning, installed state-of-the-art air filters and allowed in-flight staff to wear face masks.

For example, Cathay Pacific now replaces used pillows, blankets, headset covers and headrest covers, spokeswoman Carolyn Leung said.

China Southern Airlines has been disinfecting the cabins of all aircraft. China Eastern Airlines flight attendants are required to wear disposable face masks, gloves and hats and even disposable overcoats during flights to some destinations.

Mexicana Airlines uses high-efficiency filters that can trap small particles that would normally recirculate back into the air, spokesman Adolfo Crespo said.

The H1N1 flu virus has been confirmed in 20,000 people in 68 countries, killing at least 126, according to the World Health Organisation. Although it appears mild, experts are concerned that the disease could change into a more dangerous form.

In the wake of the spread, some countries have intensified health precautions.

Singapore saw its first case of the H1N1 flu in late May, after a native student flew home from New York on a Singapore Airlines flight.

Singapore has been thermal-screening everyone coming into the country. The method, which identifies travellers with a fever, did not help authorities spot the sick student, as she had not yet developed a fever.

The government quarantined the passenger and about 60 other people on the same flight who were sitting within three rows.

"This won't be the last case in Singapore unless we could stop people from travelling," Singapore's Health Minister Khaw Boon Wan said.

Singapore Airlines, the world's biggest by market value, is giving passengers travelling to the United States health kits that include a thermometer, masks and antiseptic towels. Its cabin and flight crews are getting mandatory temperature checks before flights.

US CARRIERS

In contrast to the measures taken by Asian airlines, US carriers have continued safety standards already in place, relying on the advice of authorities such as the Centers for Disease Control and Prevention.

Atlanta-based CDC has not recommended that airline crews wear face masks or disposable overcoats.

"The issue with H1N1 and airlines is an issue of translocation, not necessarily on-board transmission," Shelly Sikes Diaz, a CDC spokeswoman, said. She added that people were no more likely to catch the flu on a two-hour plane flight than they were sitting next to someone for a two-hour movie.

"Therefore, at this time, recommended on-board infection control measures would be similar to community infection control measures" such as frequent hand-washing, Diaz added.

David Castelveter, a spokesman with the Air Transport Association trade group, said US airlines for the most part have made no major changes in the wake of swine flu, but continued current practices that include looking for passengers with symptoms of flu, measles or other infections. He added that in-flight air filters ensure that aircraft are sanitised.

"We take our guidance from the professionals (such as the CDC) who tell us the precautions that are needed to prevent the spread," Castelveter said. "We're not taking the type of precautions that are unnecessary."

While Castelveter said media coverage of the flu has boosted awareness of airline safety procedures, Mexicana's Crespo stressed that carriers still have work to do to change public perceptions that air quality on planes is bad.

"Inside, our aircraft is cleaner than in a hospital," Crespo said.

Julian Tang, a consultant for the microbiology division at National University Hospital in Singapore, also said hygiene practices such as covering the nose and mouth when sneezing or coughing in confined areas may be the best way to limit infection.

He said safety measures such as costly air filters may be of limited use for carriers.

"This is because most of the transmission between passengers probably mostly occurs just after the sneeze/cough in the immediate vicinity of the passenger rather than after it flows through the ventilation/circulation system and back out again," he said