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Cooler weather, novelty of virus spreads H1N1

Wednesday, September 2, 2009 | 7:10 p.m. CDT; updated 11:05 a.m. CDT, Thursday, September 3, 2009

JEFFERSON CITY — A Missouri health official said that cool summer temperatures are partly responsible for the increase in H1N1 cases as students head back to the classroom.

Temperatures across Missouri this summer were some of the coolest on record. In Columbia, this summer 's temperatures were the ninth coolest on record.

As winds pushed down cooler air from Canada, temperatures dropped and the air became less humid.

Eddie Hedrick, emerging infections coordinator for the Department of Health, said viruses use their pointy exterior as a means to attach to a cell's receptors.

"The dryer air seems to make it more conducive to sticking," he said. "If it's humid spikes try to attach to the cell, but if that's a slippery slope, it has trouble attaching."

As winter approaches and the weather becomes dryer, the H1N1 "swine flu" virus will find it easier to infiltrate human cells.

Although most diseases have petered out by the time summer's high temperatures and humidity roll++++ around, H1N1 spread quickly because it presented a different combination among the 144 possible combinations of  hemagglutinin and neuraminidase, two components that make up the flu virus.

"Seasonal flu are viruses that have been around for a while, circulating for generations. Your immune system has been exposed to them for some time," Hedrick said.

Very few people have any immunity to H1N1, except for about 30 percent of the 65 and up age group that have some antibodies to the virus from previous exposure to a similar virus, Hedrick said.

"We know it's no worse than seasonal flu except it's harming some people we don't normally see harmed," Hedrick said.

The average age of those infected is 12, the average age of those hospitalized is 20, and the average age of those who have died from H1N1 is 37, Hedrick said.

Even so, the fatality rate of H1N1 remains at .4 percent. During the Spanish flu epidemic of 1918, the fatality rate was 2.5 percent.

The rate of contagion of H1N1 is similar to other seasonal flu viruses. Each person infected is likely to infect another one or two people, Hedrick said.

"We're anticipating a two-fold increase in the number of flu we see (seasonally)," Hedrick said, adding that countries in the southern hemisphere have ably handled the influx of flu cases.

"They've been able to weather the storm without overwhelming their resources," Hedrick said.

A vaccine for H1N1 isn't available yet, but Centers for Disease Control and Prevention officials have said one should be ready by mid-October.

The H1N1 vaccine will require two shots to be administered three weeks apart.

"Only two weeks after the second shot will you have immunity," said Lisa Barrios, an H1N1 guidance development leader for the CDC. "People who get it are not going to have much immunity until Thanksgiving."

In the meanwhile, like with the seasonal flu, routine hand washing and cleaning are effective in preventing the virus.


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