Summer hasn't curtailed flu, say health experts
Heat and humidity usually reduce cases, they said. School reopening could bring an increase.
The pandemic swine-flu virus unexpectedly is continuing to spread easily through the United States during the summer months, and health authorities expect a bump in transmission in about six weeks, when school goes back into session - perhaps two or three months earlier than is normally seen with seasonal flu.
"Every year, there is an increase in flu when children go back to school," Anne Schuchat, director of the Centers for Disease Control and Prevention's National Center for Immunization and Respiratory Diseases said Friday in a telephone news conference, noting that viruses are being shared in close quarters. "This year, it is already circulating in summer camps, military units and so forth, so we are expecting when school opens we will see [a bigger than normal] increase."
Schuchat said she thinks the unusually high rate of transmission during the heat and humidity of summer, which normally sharply reduce transmission, may be due to the large number of Americans with no resistance to the virus from previous exposure.
As of Friday morning, the CDC reported more than 40,000 laboratory-confirmed cases of the virus (formally called H1N1), 4,800 hospitalizations and 263 deaths. Experts, however, believe that more than one million Americans have been infected.
The World Health Organization, which has reported nearly 100,000 confirmed cases worldwide, said Thursday that it would stop counting cases because that required too much unnecessary work by health authorities. The agency had said a week earlier that it recommends local agencies no longer test for the virus unless they have not had cases previously or there is an unusual outbreak.
Schuchat said the CDC probably also would stop reporting cases soon, focusing instead on more traditional measures of spread, such as pneumonia cases and deaths.
The WHO also said last week that it is recommending that the priority for immunization with a pandemic influenza vaccine should be health-care workers, both because they are at highest risk due to their exposure to patients and because infected workers could spread the virus to those at high risk. Beyond that, the agency said individual countries should set their own priorities for other groups, vaccinating schoolchildren if their goal is to limit transmission or vaccinating high-risk groups if their goal is to limit illness and deaths.
Schuchat said the CDC's vaccine advisory committee will meet this week to set this country's priorities. The Obama administration, however, has said that it will make the vaccine available to schoolchildren at no charge, budgeting as much as $7.5 billion for the effort.
Jesse Goodman, acting deputy commissioner of the Food and Drug Administration, said at the same news conference that no vaccine for H1N1 will be available until well after school has begun. Companies and the National Institutes of Health are still planning clinical trials for the pandemic vaccine, and it will be at least two months after the start of such trials before any data are available, he said.
There have been fears that a vaccine might not be available at all. The handful of companies that produce the vaccine have been inundated with orders, and some, such as Baxter International Inc., have said they are unable to accept any further orders.
Because the vast majority of vaccine production is done overseas, some experts have speculated that a shortage of the vaccine will lead the countries where it is produced to limit exports so that their own populations will have enough.
Schuchat, however, said health authorities are not worried about such a possibility. "We are not concerned about meeting expectations for the vaccine. We haven't gotten any information that makes us question the supply."