Even as the World Health Organisation acknowledged that the H1N1 swine flu virus can no longer be contained as it had spread far and wide, it gave a clean chit to India on Thursday, saying the country has not reported any swine flu case and is prepared to handle a possible outbreak.

The WHO in Geneva on Wednesday night raised the pandemic alert for swine flu by one level to Phase 5. This declaration by WHO director general Margaret Chan is a strong signal that a pandemic is imminent, but not inevitable. The second-highest phase is characterised by human-to-human spread of the virus in at least two countries in one WHO region.

At the same time, India kicked off a massive containment exercise, screening all international passengers coming from the US, Canada and Mexico for the virus.

In Goa, officials are trying to track down British tourists who arrived there after the deadly outbreak. At the same time in Hyderabad, a non-resident Indian who landed from Texas with suspected symptoms of swine flu has not turned up at a government-run hospital despite the advice of doctors. Now the health authorities are keeping a watch on him.

The 26-year-old man failed to turn up at Andhra Pradesh Government Chest Hospital, the nodal centre to deal with such cases. The officials of medical and health department are trying to convince him to undergo necessary tests at the hospital, which has the required wherewithal including four rooms for quarantine.

"There has been no suspected case in India," J P Narain, director communicable disease in the WHO regional office for Southeast Asia, told reporters. Asked about the NRI cae in Hyderabad, has been found with the flu symptoms, he said, "We spoke to the Indian health officials and they told us that the laboratory results of the man were negative."

Officials in India have also decided to increase the country's reserves of the antiviral drug Tamiflu. The health ministry has decided to stockpile three million doses of the only known drug found to be effective against the virus, as a precautionary measure.

Domestic pharmaceutical companies including Cipla, Ranbaxy, Roche and Hetero Drugs have assured the government that they would be able to supply sufficient quantities of oseltamavir, the main ingredient of Tamiflu.

Narain said there is a "strong signal that a pandemic is imminent" but added that "India is quite prepared and has the capacity to deal with any outbreak. We have the surveillance in place."

However, the swine flu scare may adversely impact investment and business confidence in India, the research arm of rating agency Moody's said on Thursday. "The swine flu scare will likely weigh on wider economic activity such as household consumption and business investment," Sharman Chan, an economist with Moody's Economy.com, said.

"Tourism and trade, which already began to show signs of fatigue in the December quarter, may experience a further blow. Asset prices are bound to retreat if the outbreak worsens and discourages investment," Chan added.

According to Moody's Economy.com, although India itself may not have upset investors, a general decline in confidence worldwide could spark repatriation of funds from stock markets. "This will not only be a drag on stock prices, but will again exert downward pressure on the rupee," Chan added.

In Mexico, the epicentre of the outbreak, there have been close to 160 deaths and nearly 2,500 infections due to the disease. Of the infected cases, more than 1,300 are in hospital, but most have not yet been identified as swine flu cases. Apart from Mexico, WHO reported confirmed swine flu cases in Canada, the US, Israel, Spain, Britain and New Zealand. Costa Rica also reported two confirmed cases.