Federal health officials now say that 4,000 or more Americans likely have died from H1N1 flu -- about four times the estimate they've been using.
The new, higher figure was first reported by The New York Times. It includes deaths caused by complications related to H1N1 flu, including pneumonia and bacterial infections.
Until now, the Centers for Disease Control and Prevention had conservatively put the U.S. H1N1 flu death count at more than 1,000. Officials said this week they're working on an even more accurate calculation.
The CDC says "many millions" of Americans have caught the pandemic flu virus since it first appeared in April.
A flu drug expert says details about North America's first reported case of pandemic H1N1 viruses resistant to Tamiflu underscore the risk of giving the drug to people to prevent them from getting ill.
Dr. Guy Boivin of Laval University in Quebec City is reporting on the case in this week's New England Journal of Medicine.
A man with chronic lung disease was given the drug to prevent him from getting sick after his 13-year-old son contracted H1N1 in late June. Within 24 hours of starting the drug the man started experiencing the symptoms of flu, suggesting he was sick when he started taking the drug.
A half dose of the drug is used to prevent illness but if a person is already sick a half dose can spur the virus to develop resistance.
Boivin says if doctors do give people Tamiflu to prevent flu they should monitor them and switch them to a full treatment dose if they become ill.
-- The Canadian Press