WHO Warns of Possible Pandemic as Mexico Seeks to Contain Swine Flu

While Mexico's flu season is usually over by now, health officials noticed a sizeable uptick in flu cases in recent weeks. The World Health Organization reported about 800 cases of flu-like symptoms in Mexico in recent weeks, most of them among healthy young adults, with 57 deaths in Mexico City and three in central Mexico, The New York Times reported Friday.

That could be worrisome. Seasonal flus usually strike hardest at infants and the elderly, but pandemic flus -- such as the 1918-19 Spanish flu, which killed an estimated 20 million to 40 million people worldwide -- often strike young, healthy people, the newspaper reported.

Schuchat said Thursday that the virus in the United States is influenza A N1H1 mixed with swine influenza viruses. The virus contains genetic pieces from four different flu viruses -- North American swine influenza, North American avian influenza, human influenza viruses and swine influenza viruses found in Asia and Europe, she said.

"That particular genetic combination of swine influenza viruses has not been recognized before in the U.S. or elsewhere," Schuchat said.

The viruses found in the United States are resistant to two antiviral medications -- amantadine and rimantadine -- but are susceptible to the antivirals oseltamivir (Tamiflu) and zanamivir (Relenza), Schuchat said.

Swine flu is a respiratory disease of pigs caused by type A influenza. Swine flu does not normally infect humans. However, human infections do occur, usually after exposure to pigs. Symptoms resemble those of the regular flu, including sore throat, coughing and fever.

Dr. Marc Siegel, associate professor of medicine at New York University School of Medicine, said the current outbreak was unlikely to become a pandemic. "Swine flu could cause the next pandemic, but it is not likely that this thing is going to erupt and take over the world," he said. Even though the virus is being transmitted human-to-human, "that's a far cry from becoming a pandemic," he added.

Dr. Martin J. Blaser, chairman of the Department of Medicine at New York University Langone Medical Center in New York City, also believes it's unlikely the outbreak will trigger a pandemic.

"The CDC has been doing more surveillance for flu," Blaser said. "So it could be that these cases have been happening all the time, but we just never saw them. Or it is possible that it is a new strain of influenza that is emerging or it's a dangerous new combination. That's why we have to watch it closely."

More information

For more on swine flu, visit the U.S. Centers for Disease Control and Prevention.