Your Family Physician

May 11, 2009 — The World Health Organization (WHO) and the US Centers for Disease Control and Prevention (CDC) are both reporting ongoing spread of the influenza A (H1N1) virus, and both agencies caution against thinking that the pandemic is losing steam.

"We believe there is sustained community transmission, person-to-person in 2 countries in 1 region, which is North America," said Keiji Fukuda, MD, MPH, assistant director-general ad. interim for health security and environment at the WHO.

"We cannot predict the future, so it is possible that we will go up to phase 6...but it is also possible for the current situation to stabilize where it is now and then it is possible that we would go back down to phase 4 in the future," Dr. Fukuda said today at a media briefing. "Most community transmission is taking place in Mexico and the United States, but not elsewhere in the world," he added.

The WHO continues to see an increase in H1N1 influenza cases being reported by countries. As of 2 am EDT, 4694 laboratory-confirmed cases from 30 countries were reported, including the first case in China. A total of 53 deaths have been reported.

Stituation Still Evolving

The WHO has repeatedly been asked whether this is a "mild event," Dr. Fukuda noted. "And we have responded by saying, 'we are not sure right now — the situation is evolving,' " he said.

He added that "most people who get infected develop mild illness, but in fact, some people develop serious illness and some of the people die," he said. "And we know that among those people who develop serious illness and who die, we know that many of them are young healthy adults."

To try to get a sense of the differences in severity among countries, one of the things the WHO is doing is to focus more on the disease impact on people, which is the parameter that is "most easy to compare from country to country," he said.

Third American Death Reported

At a CDC media briefing today, Anne Schuchat, MD, director of the CDC's National Center for Immunization and Respiratory Diseases, noted that in the United States, 3300 probable and confirmed cases in 46 states and Washington, DC, have been reported, with 2600 confirmed cases in 43 states and Washington, DC. To date, there are 3 known fatalities, 2 in Texas and 1 in Washington state, all 3 of whom had underlying medical problems. A total of 94 confirmed H1N1 influenza cases in the United States have required hospitalization.

According to Dr. Schuchat, 116 CDC personnel have been deployed. In addition, 5 virus isolates have been sent to 8 labs to identify which would be best to develop into a vaccine.

The CDC continues to receive about 300 to 400 specimens a day for testing, but few states currently have significant backlogs, she said.

"The numbers tell us for sure that this virus is circulating throughout the United States and it's likely that it's found in every state," Dr. Schuchat said. "The numbers tell us that more people have become ill and more people are likely to become ill, but we continue to see that most people who are becoming all with this virus tend to recover."

The CDC estimates that among the various forms of influenza circulating in the United States, about 40% are currently of the influenza A (H1N1) strain.

Moving Toward Use of Epidemiologic Systems

According to Dr. Schuchat, the CDC is moving toward less of a focus on the individual numbers and more toward reporting H1N1 cases using epidemiologic systems set up for seasonal influenza, such as the weekly "FluView" surveillance report.

"I think there's a perception out there that we are winding down, that we're in a lull," she said. "It's a time where we really need to guard against complacency...and we don't know what will happen come the fall."

A report in the May 15 issue of Science uses surveillance data to create a picture of the H1N1 influenza outbreak to date. "Our early analysis would suggest this is going to be an outbreak comparable to that of 20th-century pandemics regarding the extent of its spread — it's very difficult to quantify the human health impact at this stage, however," noted study author Prof. Neil Ferguson of Imperial College London, United Kingdom, in a news release.

The authors estimate that between 6000 and 32,000 infections occurred in Mexico by April 30 and that the death rate is between 0.4% to 1.4%. The outbreak seems to have started in mid-February in the village of La Gloria, Veracruz.

Source : http://www.medscape.com/viewarticle/702657?sssdmh=dm1.470812&src=nldne