New Estimates Say Swine Flu in U.S. Worse Than Thought

Jon is a staff writer for Science.

Martin is a contributing news editor and writer based in Amsterdam

First the bad news: Revised estimates from the U.S. Centers for Disease Control and Prevention suggest that the novel H1N1 virus has spread much further in the country and taken a far greater toll than earlier analyses suggested.

Now here’s some more bad news: CDC says manufacturers delivered far less pandemic vaccine this week than predicted.

According to new CDC estimates released today, about 22 million Americans have been infected with the virus, 98,000 have been hospitalized, and 3900 have died. Those data account for cases since the pandemic surfaced in April and run through 17 October. Until now, CDC has been reporting only H1N1 cases and deaths confirmed by lab tests. (As of 31 October, the cumulative numbers were 26,917 hospitalizations and 1265 deaths.) But confirmed cases are believed to be only a small portion of the true influenza burden. Many people never seek medical attention, and even if they do, they are not usually tested for the novel H1N1 virus. Some patients even die in hospitals from complications of an infection without making it into the statistics

Anne Schuchat, head of CDC’s National Center for Immunization and Respiratory Diseases, explained at a press conference today that the new estimates come from improved methodology that does not strictly rely on laboratory-confirmed cases. “We don’t think things have changed from last week to this week,” said Schuchat. “For influenza, it’s virtually impossible to find every single case with a lab test."

In the new methodology, CDC extrapolates from two sources of information: the Emerging Infections Program that tracks lab-confirmed cases of pandemic H1N1 influenza in 10 states and the Aggregate Hospitalization and Death Reporting Activity that Schuchat said has reporting from about 30 states. “The estimation method we are using now we believe gives a bigger picture, probably a more accurate picture of the full scope of the pandemic,” she said.

As for vaccine supplies, CDC says the total made available to states as of today is 41.6 million doses. Last Friday, the total was 38 million and CDC expected to have 8 million more by the end of this week. “We aren’t expecting to meet that estimate that the manfacturers gave us,” said Schuchat. When asked what accounted for the delays, Schuchat pointed to the final stage of vaccine testing and transportation issues because of bad weather.

Meanwhile, the World Health Organization today stressed that antiviral treatment should start as early as possible in H1N1 patients who are at higher risk of severe disease. Waiting too long before administering Tamiflu or Relenza in pregnant women, children under 2 years of age, and people with lung or heart conditions not only can be fatal, but also leads to more stress on overburdened health systems, WHO Medical Officer Nikki Shindo warned today during a press briefing from Geneva. The recommendations are part of new guidance on how to treat H1N1 patients.

"We have heard that doctors caring for very sick patients in intensive care units regretted that patients arrived too late, and even the most sophisticated medical procedures could not save their lives," Shindo said. With at-risk patients, doctors should not wait for lab confirmation that a patient has H1N1, and they should treat even if symptoms are mild. "The window of opportunity is very narrow to reverse the progression of the disease. The medicine needs to be administered before the virus destroys the lungs." Although Tamiflu is most efficacious when given within 48 hours after the onset of symptoms, doctors should not withhold the drug if that window has passed, she added, because it can still have benefit.

WHO has a stockpile of 10 million Tamiflu treatment courses for use in developing countries, and Shindo said that the agency is trying to get donors to provide more. Recently, part of the stocks were distributed to Afghanistan, Mongolia, Belarus, and Ukraine, which have been hit hard; Azerbaijan and Kyrgyzstan will soon follow.

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