Pandemic is on the Way

June 11, 2009 — The World Health Organization (WHO) has increased the pandemic level to phase 6, the final alert phase, indicating that a global pandemic of influenza A (H1N1) is under way.

According to the WHO, pandemic alert level phase 6 is characterized by "community level outbreaks in at least one other country in a different WHO region in addition to the criteria defined in Phase 5." Phase 5 is characterized by human-to-human transmission of the virus into at least 2 countries in 1 WHO region.

After holding an emergency meeting with its influenza experts, the WHO said it has raised the pandemic warning level from phase 5 to 6, according to a statement sent to health officials. WHO Director Dr. Margaret Chan made the announcement during a press conference today.

Scientific Criteria Met

"The world is now at the start of the 2009 influenza pandemic," she said. "The scientific criteria for a pandemic has been met."

According to Dr. Chan, further spread is considered inevitable, "but no previous pandemic has been detected so early or watched real time right at the very beginning."

"The virus is stable" and it looks very similar among countries, Dr. Chan said. "We need to continue to check this virus and monitor it. We should never forget...we still have H5N1 in phase 3 pandemic alert status, and this is the first time we have 2 viruses coexisting...it is an extremely unusual situation."

She added that the virus can change the rules without rhyme or reason at any time, and it will be important to see how the virus changes as it returns to the Northern hemisphere in the fall.

The H1N1 virus is of "moderate severity" with most people making a rapid and full recovery often in the absence of treatment, and the number of deaths is small.

She pointed out that pregnant women are at increased risk for complications, and the virus preferentially infects younger age groups, under age 25 years. She added that it is unknown how this virus will behave under conditions in the developing world. The WHO says that it continues to put no restrictions on travel.

Because of the susceptibility of the population, "influenza pandemics are remarkable events," she said, "but we are all in this together."

As of today, the WHO is reporting nearly 30,000 confirmed cases from 74 countries.

Pandemic Level Increase "Not a Surprise"

At a press briefing immediately after the WHO announcement, Thomas R. Frieden, MD, MPH, who assumed the role of US Centers for Disease Control and Prevention (CDC) director on Monday, commented on the WHO's decision, stating that the increase to pandemic level phase 6 was "not a surprise" and that it was "expected based on the data."

According to Dr. Frieden, the WHO waited until they were certain that they had documentation that on multiple continents that the virus was being transmitted from person to person in a sustained way and this "basically meets our definition of a pandemic."

The key goals are to determine where the virus is spreading and to reduce its impact, "particularly on those who are most vulnerable — people with underlying health conditions and infants as well in this case," he said.

Also at the briefing, Anne Schuchat, MD, the interim deputy director for science and public health program and director of the CDC's National Center for Immunization and Respiratory Diseases, noted that there are more than 13,000 confirmed cases reported in the United States.

"There are over 1000 people who have been hospitalized that have been reported to us, and our last update on the counts of death are 27, but we'll be updating that soon and I do, unfortunately, expect that number to rise," she said.

According to Dr. Schuchat, increases in influenza cases above normal levels for this time of year are still being observed in region 1 (New England) and region 2 (New York and New Jersey).

CDC Was Responding as if to Pandemic Already

"People think it is over, but we need to remain vigilant," she said. However, she pointed out that the CDC has been "reacting as though we were in a pandemic already in terms of our intensive efforts to prepare individuals and respond as a nation."

According to Dr. Schuchat, 57% of the cases have occurred in people aged 5 to 24 years, and 41% of hospitalizations were also within that age range. The highest rates of hospitalizations are in children younger than 5 years. Of the hospitalizations, 71% have occurred in people with an underlying condition.

"As we have noted, there's been a disproportionate amount of pregnant women among those who have had infection," she said.

"What this declaration does do is remind the world that flu viruses like H1N1 need to be taken seriously," Health and Human Services Secretary Katherine Sebelius said in a news release today.

"Although we have not seen large numbers of severe cases in this country so far, things could possibly be very different in the fall, especially if things change in the Southern hemisphere, and we need to start preparing now in order to be ready for a possible H1N1 immunization campaign starting in late September," she noted.