CDC fears more swine flu cases in fall

A microbiologist tests samples for Influenza A (H1N1), formerly referred to as swine flu, at the Dallas Department of Health and Human Services laboratory in Dallas, Texas May 1, 2009.

CHICAGO/WASHINGTON (Reuters) - The new H1N1 swine flu virus is still circulating and will likely cause more disease in the fall, when schoolchildren return from summer break, a U.S. Centers for Disease Control and Prevention official said Friday.

The virus, which has been declared a pandemic, is causing severe disease and deaths in older children and younger adults in the Southern Hemisphere, just as it has in the United States, the CDC's Dr. Anne Schuchat said.

"We are expecting an increase in influenza or respiratory illness that could be earlier than what we see with seasonal influenza," Schuchat told reporters in a telephone briefing.

"This year we've been seeing this 2009 H1N1 influenza virus circulating in the summer months. We've seen it in camps and military units. I'm just expecting when school reopens and kids get back together, we expect to see an increase."

Schuchat said the virus, which officials estimate has infected millions of people, was thriving in spite of the heat and humidity of summer. Usually respiratory viruses such as flu do not circulate well in summer months.

Schuchat said this was probably because so many people do not have immunity to H1N1, and not because the virus has some unusual biological properties.

Pregnant women also often have more serious symptoms and are more likely to die, just as with seasonal flu, Schuchat said. The same pattern is being seen in Southern Hemisphere countries like Argentina, she said.

The virus has spread fast, Schuchat said. "We have seen this virus reach every country in a matter of weeks and months and not years," she said.

MANUFACTURING PROBLEMS

Thursday, Baxter International, one of the companies making H1N1 vaccine for the U.S. market and four other countries, said Thursday it could not take any more orders.

But Schuchat said she was not worried.

"We're on track and not concerned about not meeting expectations," she said. "We haven't gotten information that makes us question the supply that has been promised.

Four other companies make flu vaccines for the U.S. market -- GlaxoSmithKline Plc, Novartis AG, Sanofi-Aventis SA and AstraZeneca, through its MedImmune unit.

Some companies have said they are not able to make as much vaccine as they had hoped because of the way the virus grows in eggs.

"Based on what has been described to us so far, it has been in the range of our planning assumptions, but that doesn't mean we won't see more surprises," Schuchat said.

WHO has said new samples of virus are being sent to companies to see if they grow better in eggs.

Tests of the new H1N1 vaccine are likely to get underway in August and Schuchat and other officials stressed that these tests in people will be crucial to knowing how much vaccine will be needed -- and available.

"We do not know how effective an H1N1 vaccine will be in different populations," Schuchat said.

The CDC said more than 40,000 people had been confirmed infected with H1N1, with 263 deaths. But the World Health Organization said Thursday the flu was too widespread to make counting individual cases possible or useful and Schuchat said the CDC was considering changing the way it reported on the spread.

Most people infected with H1N1 are never tested, so any count of confirmed cases only represents a fraction of the true