Vail doc: Do you know your (influenza) alphabet? | VailDaily.com
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Vail doc: Do you know your (influenza) alphabet?

Dr. Drew Werner
Vail, CO

Dear Doc,

I’ve heard that there will be a vaccine for the swine flu. When will it be available and where can I get it?

– Staying healthy in Vail,

Dear Healthy,

Your question is a good one and certainly a hot topic now. Unfortunately, clear answers and concise guidelines are still pending. Some background information may help understand our current situation.

Influenza, which we all know as the flu, is actually a family of viruses called orthomyxoviridae. These viruses infect both birds and mammals. These viruses have a remarkable ability to evolve or change, which is how they survive. Each time they change, they become less susceptible to the natural defenses our bodies built when we were exposed or had were immunized the year before.

Even more complex is the ability of the influenza viruses to combine with a completely different strain of the virus to which we have no immunity. The result is often a pandemic, or a worldwide spread of influenza, that infects a large portion of the population.

Each century sees two or three pandemic flus. In the 1900s, we saw three. The Hong Kong Flu in 1968., the Asian Flu in 1957, and the granddaddy of them all, the Spanish Flu of 1918 in which one third of the population on earth was infected and between 50 million and 100 million people died.

A sobering thought is that 25 million people died in the first 25 weeks of the 1918 Influenza pandemic, while 25 million people have died from HIV. While the exact origins of that flu are not known, it is believed it may have been a strain of bird flu and distant relative to the current H1N1 causing so much illness now.

Influenza A is identified by its two antigens (an HA antigen and an NA antigen). There have been 16 different HA antigens identified and nine different NA antigens. There are also differences in the specific antigen groups resulting in the year to year variability in infectiousness.

The seasonal flu, which arrives every fall to spring, is typically caused by a strain of influenza A H3N2, and seasonal H1N1 (which is actually quite different from the current pandemic version of H1N1). A strain of Influenza B also contributes to seasonal flu but because it evolves much more slowly, it is less responsible for widespread severe illness. The “flu shot” protects against all three of these seasonal flu strains.

Pandemic H1N1 is different altogether. It is a strain of influenza that infected pigs and only recently combined with a human strain of flu allowing it to cause human-to-human transmission. Unlike H5N1, or avian flu, which has not been a significant cause of human-to-human infection, H1N1 has been identified world wide, resulting in our current pandemic.

Another significant difference from seasonal flu is in the population of people getting very sick or dying. While seasonal flu is still the most dangerous to the very young and old, pandemic H1N1 is dangerous to those in between, especially young people in their teens, 20s and 30s. For that reason, the recommendations for who should receive the upcoming H1N1 vaccine will be different than the seasonal flu vaccination recommendations.

Perhaps most importantly, don’t get in line yet. While a vaccine is being developed, it is not quite ready and the Centers for Disease Control has made it clear that the H1N1 vaccine will not be released until it is fully ready. At the same time, this vaccine, unlike the seasonal vaccine, will be available only in limited quantities initially.

In any case, it will be very important to get your regular seasonal vaccine as soon as it is ready to be given. The CDC is recommending that anyone who wants to minimize their chance of getting seasonal flu should get the regular seasonal flu vaccine. There should be plenty available for everyone.

I will keep you updated in the coming weeks, especially as guidelines and recommendations may change regarding H1N1 and its vaccine. Until then keep washing your hands, cover your coughs and, most importantly, if you are sick with fevers, cough and nasal congestion stay home.

Dr. Drew Werner is the vice chief of staff at Valley View Hospital in Glenwood Springs and the Eagle County Health Officer. He lives in Eagle with his family. E-mail comments about this column to cschnell@vaildaily.com.


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