By Dr. Katherine Seibert Published: 2:00 AM – 12/07/11

Influenza viruses Types A and B cause annual outbreaks of flu affecting approximately 5-10 percent of adults each year, with higher rates in children.

There are multiple varieties of A and B viruses; the swine origin H1N1 virus is one of the Type A viruses. in the United States, influenza causes an average of more than 36,000 deaths per year and more than 130,000 hospitalizations.

People over age 65 constitute about half of the excess hospitalizations from the flu and more than 85 percent of the deaths.

However, in the U.S., most people who become ill with the flu recover without requiring any medical treatment. the flu occurs annually in this climate between December and March.

The flu virus changes its surface proteins so fast that no one becomes fully immune. This year’s virus is not a carbon copy of last year’s, thus necessitating a change in the composition of the yearly flu vaccine.

Symptoms of the flu come on abruptly, and usually include fever, chills, headache, fatigue, muscle aches and loss of appetite. Sore throat and dry cough may occur early in the illness. Secondary bacterial pneumonia can follow within one to three days, with rapidly progressing symptoms.

Influenza is thought to spread mainly person to person through coughing or sneezing by infected people. it may also be spread by touching infected objects, such as a phone, then touching one’s nose or mouth.

In many circumstances, the diagnosis of influenza can be made clinically. Several laboratory tests are available, but viral cultures do not yield timely results. Rapid antigen tests are available, but sensitivities are variable, between 60 and 90 percent. Specimens for influenza testing are aspirates and swabs from the nasopharyngeal area.

The flu is often treated symptomatically with rest and fluids. People who are at high risk of serious complications from influenza may benefit most from antiviral medications. Several antiviral drugs are available for treatment of influenza. These antivirals, if begun early, will reduce the duration of fever and symptoms by one to three days and provide more rapid overall recovery.

Little or no benefit is seen when treatment is initiated two days or more after the onset of uncomplicated influenza symptoms. the greatest effect occurs when antivirals are begun within the first 24 hours.

Influenza vaccines are available in two forms:

Flu vaccine protection is recommended for all persons 6 months old and older. the intranasal vaccine is currently approved only for healthy people ages 2-49 who are not pregnant.

Administration of the inactivated vaccine is associated with arm soreness in about one-third of people, and other side effects are infrequent. Adequate immunity is achieved in about two weeks after vaccination, and it is very effective in preventing the flu.

To protect yourself and others from the flu, it is important to follow good hand-washing and hygiene practices.

If you become sick with flu-like symptoms, stay at home for least seven days after the onset of illness or until 24 hours after your symptoms resolve, whichever is longer.

Katherine Seibert, M.D., Ph.D., FACP, is a practicing internist who sees patients at Hudson River HealthCare in Monticello. she is also a doctor of microbiology and a Sister of Charity of new York. she has been serving Sullivan County as a physician for the past 20 years.

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Avian influenza: Also called fowl plague, avian flu, and bird flu. Ahighly contagious viral disease with up to 100% mortality in domestic fowl.Caused by influenza A virus subtypes H5 and H7. all types of birds aresusceptible to the virus but outbreaks occur most often in chickens and turkeys.The infection may be brought by migratory wild birds which can carry the virusbut show no signs of disease. Humans are only rarely affected.

Type A influenza viruses can infect several animalspecies aside from birds, including pigs, horses, seals and whales. Birds are anespecially important species because all known subtypes of influenza A virusescirculate among wild birds, which are the natural hosts for influenza A viruses.Avian influenza viruses do not usually directly infect humans or circulate among humans.

Influenza A viruses can be divided into subtypes on thebasis of their surface proteins – hemagglutinin (HA) and neuraminidase (NA). There are 15 known H subtypes. While all subtypes can be found in birds, only 3 subtypes of HA (H1, H2 and H3) and two subtypes of NA (N1 and N2) are known to have circulated widely in humans.

The symptoms in humans range from typical influenza-like symptoms (with fever, cough, sore throat and muscle aches) to eye infections, pneumonia, acute respiratory distress, viral pneumonia, and other severe and life-threatening complications.

Studies to date suggest that the prescription medications approved for human influenza strains would be effective in preventing avian influenza infection in humans.

All influenza viruses have the potential to change. Itis possible that an avian influenza virus could change so that it could infecthumans and could spread easily from person to person. Because these viruses donot commonly infect humans, there is little or no immune protection against them in the human population. if an avian virus were able to infect people and gain the ability to spread easily from person to person, an influenza pandemic, a global outbreak, could begin.

Past influenza pandemics have led to high levels of illness, death, social disruption and economic loss. There were 3 pandemics in the 20th century; the Spanish flu (1918-19), Asian flu (1957-58), and Hong Kong flu (1968-69). all of them spread worldwide within a year of being detected.

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