H1N1 swine flu still around, CDC says

WASHINGTON (Reuters) - H1N1 swine flu continues to cause epidemics, especially in the southeast of the United States, U.S. federal researchers reported on Thursday.

Americans who have not been vaccinated should still try to get the shot or nasal spray, the team at the U.S. Centers for Disease Control and Prevention said.

The CDC's weekly surveillance report on influenza mirrors the World Health Organization's warning that the pandemic continues, although at low levels. As long as the virus is being passed among people, it could change and re-emerge at any time, infectious disease specialists say.

"For the week ending March 27, 2010, pneumonia or influenza was reported as an underlying or contributing cause of death for 7.9 percent of all deaths" in the United States, the CDC said. This is slightly above the epidemic threshold of 7.8 percent that the CDC has set for the last week of March.

More than half the reported cases were in Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, and Tennessee.

Children were the hardest-hit, in contrast to seasonal influenza, which is usually worst among the elderly.

"This season's cumulative hospitalization rates from August 30, 2009, through the week ending March 27, 2010, remain highest in children aged 0-4 years," the CDC said.

Earlier this week John Mackenzie of the WHO's Emergency Committee said the H1N1 flu pandemic is as severe as influenza pandemics in 1957 and 1968 -- which killed 3 million people between them.

The CDC estimates that H1N1 has killed 12,000 Americans and put more than 265,000 in hospital.

Between 81 and 91 million doses of influenza vaccine have been administered of the 162 million doses shipped across the country, the center said.

Early in the pandemic, there were long lines of people clamoring for H1N1 vaccines but there was not enough to go around. By the time vaccines were available in ample supplies, most of the public had lost interest.

The United States has contracts with five influenza vaccine makers -- Novartis, AstraZeneca unit MedImmune, Sanofi Aventis, GlaxoSmithKline and Australian vaccine maker CSL.

(Reporting by Maggie Fox, editing by Anthony Boadle)