The suspected case in South Korea involves a woman who has recently returned from a trip to Mexico.
Officials at Seoul's Centre for Communicative Disease Surveillance and Response said the 51-year-old woman from Gyeonggi province was undergoing tests.
'Caution and concern'
"Currently, laboratory tests are underway," Jun Byung-yool, the director-general, told a press conference on Tuesday. "Test results will be available as early as Wednesday morning."
|Asia has previously battled deadly viruses such as the H5N1 bird flu and SARS [Reuters]
He said the woman was staying at home in isolation and has been given special masks and given injections of Tamiflu, a drug used previously to treat bird flu virus infections.
In New Zealand health officials said that at least 56 people with flu-like symptoms, all of whom had returned from Mexico or the US in the past two weeks, are being tested for influenza A, a virus type to which swine flu belongs.
The tests follow a weekend announcement that nine teenage students and a teacher who returned to New Zealand from Mexico had tested positive for influenza A, and were suspected of contracting swine flu.
Tony Ryall, New Zealand's health minister, told reporters the latest developments signalled "a time for caution and concern, but not alarm."
In neighbouring Australia meanwhile authorities said they were investigating 17 cases of suspected swine flu which, Nicola Roxon, the health minister, said was "at least possible if not likely".
Five people, including children, had tested positive to a type A virus in the state of New South Wales, and would undergo further tests to "rule out what it might be", the minister added.
|Governments have been stockpiling drugs such as Tamiflu to treat cases [AFP]
In Asia, a continent that has battled the deadly bird flu and Sars viruses in recent years, authorities have stepped up health monitoring in an effort to ward off the swine flu threat.
Other measures include stocking up on millions of doses of anti-viral drugs and personal protection equipment such as surgical masks as well as installing thermal scanners at major airports.
In China, where officials were heavily criticised for their handling of the Sars outbreak, health authorities boosted quarantine measures and instructed hospitals to step up monitoring and testing amid fears of a swine flu outbreak in the country.
The China Daily said authorities in the southern province of Guangdong have "strengthened quarantine measures" but did not go into specifics.
Southern China has frequently been the breeding ground for diseases that jump between animals and humans because they often live in close proximity in the vast farming villages.
In Japan officials at the foreign ministry said it would temporarily tighten visa rules for Mexican citizens, meaning they can no longer obtain a visa on arrival, as part efforts to stop the virus from entering the country.
"The foreign ministry is scheduled today to order the Japanese embassy in Mexico to temporarily suspend a visa waiver programme and tighten visa screening procedures there," a Japanese foreign ministry official told AFP.
Australia, New Zealand, Taiwan, South Korea and Singapore have also issued advisories against non-essential travel to Mexico.