Pacific island nations have been warned they are more vulnerable to swine flu than other countries.
The new strain of H1N1 influenza has been detected in 19 countries worldwide, but the small South Pacific countries have so far remained virus-free.
But the World Health Organisation (WHO) has warned that if cases are reported, the impact will be worse than elsewhere.
"They have only a limited stretch of their health care systems and a limited stretch of their essential services like safe water, electricity, security and all that," WHO medical officer Dr Jacob Kool told Radio New Zealand.
"We know that in the 1918 Spanish Flu pandemic the most severely affected countries were actually in the Pacific and some of them had quite a high mortality."
Health authorities in Samoa are monitoring the flu symptoms in three people newly arrived from the United States.
Mexican officials said on Sunday that the epidemic was now "in its phase of decline".