Medscape,com, April 29, 2009, Emma Hitt The swine influenza outbreak shows no signs of slowing down, but, for now at least, the World Health Organization (WHO) has stopped short of increasing the pandemic alert level from phase 4 to phase 5.

“Phase 5 is a significant milestone, and we are trying to make absolutely sure that we are dealing with sustained transmission in 2 or more countries,” Keiji Fukuda, MD, MPH, assistant director-general ad. interim for Health Security and Environment at the WHO, said during a press conference today.

“In New York City, we are seeing a person-to-person transmission occurring in a high school, but we are looking for transmission among people in neighborhoods and communities before we move to phase 5,” he said.

The worldwide pandemic alert level was raised on Monday of this week to phase 4, which is defined as confirmed person-to-person spread of a new influenza virus able to cause “community-level” outbreaks.

According to Dr. Fukuda, as of 11:00 am EDT today, 114 cases have been officially reported to the WHO. In Mexico, 26 confirmed cases and 7 deaths have been reported, although Mexican authorities are reporting that swine flu is now suspected in more than 100 deaths and nearly 2500 illnesses. Earlier today, the first American fatality was reported — a 23-month-old toddler in Texas.

Swine Flu Mostly Similar to Seasonal Flu

Dr. Fukuda pointed out that the current outbreak is characteristic of typical seasonal influenza, with the possible exception of more diarrhea cases with swine flu than with seasonal influenza.

A WHO-led conference call of several influenza specialists across the globe was ongoing at the time of the press briefing. According to Dr. Fukuda, the discussion by participants on the conference call was helping to confirm their initial impressions of the outbreak. “There is nothing to suggest that our preliminary assessments are incorrect,” he said.

Dr. Fukuda noted that the epidemiologic evidence clearly suggests that the virus is being transmitted from person to person. “Studies are underway to look further at the transmissibility of this virus, and I expect this info to unfold over days and weeks,” he said.

He emphasized that the swine virus had moved from swine to humans, but that consumption of pork and other meats do not pose a risk. In addition, no coinfections are thought to be occurring with the swine flu infections.

Unanswered Questions

An important question that remains to be answered is the potential severity of the illness. Currently, the spectrum ranges from very mild to fatal, which is in keeping with other influenza infections. “We do not know the likelihood of developing mild vs fatal illness or the risk factors among those people who develop fatal illness,” he said. Also unknown is information about mutations that might have allowed the virus to jump from swine to human transmission.

For the most part, the virus is in keeping with normal seasonal influenza viruses, but Dr. Fukuda emphasized that it is premature to think of this as a mild or severe pandemic, since “we cannot predict what the course will be. It is possible that this epidemic could suddenly stop, but it is unlikely.”

He added that the worst pandemic of the past century, in 1918, started out mild in the springtime, was fairly quiet during the summer, and then in the fall it “really exploded into a much more severe form — so we just don’t know what the future is going to hold. The most important point now is that countries really have a warning and have time to prepare.”

Myron S. Cohen, MD, director of the Institute for Global Health and Infectious Diseases and associate vice chancellor for global health at the University of North Carolina in Chapel Hill, noted that national guidelines will be developed shortly, but “in this transitional period, individual hospitals and physician clinics certainly need to evaluate their resources and manage their practices carefully.”

“There are real decisions that need to be made on the ground,” he told Medscape Infectious Diseases in a phone interview. “Who gets a mask and who doesn’t get a mask? Who gets lab testing and who does not? Who gets [oseltamivir] or [zanamivir] and who does not?”

Dr. Cohen recommends that clinicians define potential case patients broadly, considering any patient with symptoms consistent with flu, not just those who have traveled to Mexico or who have been in contact with infected people.

According to Dr. Cohen, the outbreak could go away quickly or it could become a “sustained, pretty big problem.”

“The good news is that there is no doubt we are going to be able to make a vaccine, and so the time frame in which we will have to deal with this is only a few months,” he said. “There is a chance of resistance developing toward antiviral drugs, depending on how much the agent is used, but let’s hope that does not happen.”

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