Swine Flu Pandemic Possible

Let's see. There was the 1918 flu pandemic. More than 100 million people were killed worldwide.

There was the Hong Kong flu, which killed more than 34,000 in the United States.

Now, we're dealing with swine flu, which is typically categorized as H1N1.

Will this be the pandemic scientists and medical experts had dreaded with what they expected to be the bird flu strain or will it fizzle? No one knows. It's too soon to tell, although there are a few things that mitigate against the kind of mass death that the 1918 flu pandemic saw. For one thing, swine flu, while being extremely easy to transmit and succumb to its effects, is not nearly as deadly as other version, including the bird flu:

Swine influenza, or “swine flu”, is a highly contagious acute respiratory disease of pigs, caused by one
of several swine influenza A viruses. Morbidity tends to be high and mortality low (1-4%). The virus is spread among pigs by aerosols and direct and indirect contact, and asymptomatic carrier pigs exist. Outbreaks in pigs occur year round, with an increased incidence in the fall and winter in temperate zones. Many countries routinely vaccinate swine populations against swine influenza.

Swine influenza viruses are most commonly of the H1N1 subtype, but other subtypes are also circulating in pigs (e.g., H1N2, H3N1, H3N2). Pigs can also be infected with avian influenza viruses and human seasonal influenza viruses as well as swine influenza viruses. The H3N2 swine virus was thought to have been originally introduced into pigs by humans. Sometimes pigs can be infected with more than one virus type at a time, which can allow the genes from these viruses to mix. This can result in an influenza virus containing genes from a number of sources, called a "reassortant" virus.

Although swine influenza viruses are normally species specific and only infect pigs, they do sometimes cross the species barrier to cause disease in humans.

What are the implications for human health?

Outbreaks and sporadic human infection with swine influenza have been occasionally reported. Generally clinical symptoms are similar to seasonal influenza but reported clinical presentation ranges broadly from asymptomatic infection to severe pneumonia resulting in death. Since typical clinical presentation of swine influenza infection in humans resembles seasonal influenza and other acute upper respiratory tract infections, most of the cases have been detected by chance through seasonal influenza surveillance. Mild or asymptomatic cases may have escaped from recognition, therefore the true extent of this disease among humans is unknown.

A pandemic involving influenza has not only been overdue for years, but with the way people can travel around the world, the threat from an outbreak is multiplied and can spread far beyond the initial outbreak area in a matter of hours. It could happen far faster than authorities can react to contain the outbreak to a localized area.

Mexico City is not taking any chances. It has canceled all public events.

The World Health Organization is extremely concerned. More than 1,000 cases have been reported worldwide. It's also been found in the NY metro area as several people at a Queens, NY school have been diagnosed with suspected cases of swine flu. It's a mild version, but experts are concerned it may morph into a more virulent and dangerous form.

The students were among about 100 at St. Francis Preparatory School in Fresh Meadows who became sick in the last few days, said Dr. Thomas R. Frieden, New York City’s health commissioner.

“All the cases were mild, no child was hospitalized, no child was seriously ill,” Dr. Frieden said.

Health officials reached their preliminary conclusion after conducting viral tests on nose or throat swabs from the eight students, which allowed them to eliminate other strains of flu. Officials were also suspicious since some St. Francis students had been to Mexico recently. The samples have been sent to the Centers for Disease Control and Prevention, the only lab in the country that can positively confirm the new flu swine strain — which has been identified as H1N1 strain. Results were expected on Sunday, officials said.

Outside New York, at least 11 swine flu cases have been confirmed in the United States — in California, Texas and Kansas, where two cases were reported on Saturday. There have been no deaths and officials said most of the 11 seemed to be recovering.

The outbreak has killed at least 68 people in Mexico and infected about 1,000 others.

Fearing a panic that might tax local health facilities, Dr. Frieden urged New Yorkers not to go to a hospital if they had typical mild cold or flu symptoms. If they are seriously ill, especially with lung problems, they should seek medial attention promptly, he said, because anti-flu drugs work best if taken in the first 48 hours of symptoms.

Because of fears of the H5N1 avian flu, both New York City and the United States have had detailed pandemic emergency plans in place since 2005, as well as stockpiles of emergency supplies and flu drugs (the plan can be read at www.pandemicflu.gov).

Dr. Frieden said that for such an emergency, the city had extra hospital ventilators, huge reserves of masks and gloves and “millions of doses of Tamiflu,” an anti-flu drug that thus far appears to work against the new swine strain.

In a reaction to the flu outbreak, the World Health Organization convened an emergency meeting of experts on Saturday in Geneva, while public health officials in the United States huddled on conference calls to discuss what steps, if any, to take.

Officials with the W.H.O. were discussing whether to declare an international public health emergency, a move that could involve travel advisories and the closing of borders.

The US has a pandemic flu resource page here and maps outbreaks of all flu cases here.