Washington - The United States said the ongoing threat from swine flu, which has killed at least 33 people in the country, must be taken seriously as the World Health Organization Thursday declared the virus a global pandemic - its highest alert level. Health Secretary Kathleen Sebelius said the WHO's action had been expected as the H1N1 virus has spread to more than 70 countries around the world.
The United States has been the second-hardest hit country in the world after Mexico, where the virus originated. More than 13,000 cases have been reported in the US - most of them mild - and Sebelius warned the situation could get worse as the flu season starts up again in the autumn.
"What this (WHO) declaration does do is remind the world that flu viruses like H1N1 need to be taken seriously," Sebelius said. "Although we have not seen a large number of severe cases in this country so far, things could possibly be very different in the fall."
Health authorities in New York, the state suffering most in the US, on Thursday raised the death toll from the virus to 15 people.
Sebelius said an immunization campaign to curb the virus could be started in late September.
