The World Health Organization says the swine influenza A-H1N1 virus has infected more than 2,000 people worldwide.
The WHO says the swine flu has spread across 23 countries, though most of the cases have been reported in Mexico and the United States.
Earlier Thursday, the WHO's acting director-general Keiji Fukuda told Asian officials in Bangkok by videolink
that the WHO does not know how severe the swine flu outbreak will
become. He warned the virus could get more virulent later in the year
during the northern hemisphere's flu season.
If it turns into a pandemic, he said one third of the world's population -- up to two billion people -- could end up infected.
The United States has confirmed nearly 900 cases of swine flu, while Mexico has reported more than 1,000.