Pandemic influenza A (H1N1) numbers double from previous CDC estimates

About 50 million people have become ill with influenza A (H1N1) since the pandemic’s onset seven months ago, CDC director Thomas Frieden, MD, MPH, said during the agency’s weekly influenza update, a substantial rise from the 22 million reported last month.

The increases likely reflect late reporting and not new illnesses, according to Frieden, who said the estimates include cases that have occurred from April through November 14, 2009.

During this time more than 200,000 people have been hospitalized, about the same number normally seen during the entire year with usual seasonal influenza, and nearly 10,000 people have died from the illness. Mortality has disproportionately affected children, who account for 1,100 deaths, and adults aged younger than 50 years, who account for 7,500 deaths.

Although surveillance data during the past few weeks have shown a decline in new cases of influenza, Frieden emphasized that influenza season typically lasts until May.

“There is still a good window of opportunity to get vaccinated against H1N1 influenza,” he said. About 12 million new doses of H1N1 vaccine were manufactured last week, putting the number of available doses at 85 million, and many states have begun increasing eligibility after having met demands for the five priority groups outlined by ACIP.

“The more people who are vaccinated, the more people who will be protected from influenza, the fewer cases we’ll have in the future, the less likely we will be to have a third wave or more cases in the weeks and months to come,” Frieden said. He added that there is no way to predict what the future holds in terms of the disease, and said that if there are more cases it will likely affect different populations and geographic locales in different ways.

Underscoring Frieden’s comments, data newly published in the Dec. 11 issue of Morbidity and Mortality Report show that mortality rates among American Indian and Alaska Native populations were four times higher than all other racial and ethnic populations combined since the start of the pandemic.

Overall, H1N1 death rates from 12 different states representative of about 50% of these indigenous populations were 3.7 per 100,000 compared with 0.9 per 100,000 in all other U.S. racial and ethnic populations combined.

Officials believe that high prevalence of chronic health conditions such as diabetes and asthma, poverty and delayed access to health care may account for the disparities. “Since the beginning of the H1N1 outbreak, we’ve been aware of the potential for greater harm in populations with higher susceptibility,” Frieden said.

Previous reports have indicated that Alaska Native and American Indian adults are two-to-three times more likely to have diabetes than other U.S. adults and experience a poverty rate twice that of the rest of the nation. “We prioritized vaccine and have worked with states to insure that the Indian Health Service and other facilities that care for American Indians and Alaska Natives get enough vaccine and treatment early on to reduce the burden of illness and death to the greatest extent possible within existing technology.”– by Nicole Blazek

For more information:

CDC. MMWR. 2009;58:1341-1344.