The health ministry said a special team had been deployed at Colombo's international airport to screen visitors from Mexico, United States, Britain, Spain, New Zealand and Canada, and 'thermal scan' machines would be deployed there.
The statement said the disease may start with fever, coughing, breathing difficulties and progress onto lung infections, which could be fatal.
The World Health Organization has warned of a significant increase in the risk of a pandemic with the United States Wednesday reporting the first death outside Mexico, which has 159 suspected swine flu fatalities.
New Zealand, the only country in the Asia Pacific region with confirmed cases, announced three more likely ones on Wednesday, taking the country's total of probable and confirmed infections to 14.