Influenza A Virus Subtype H5N8

The family of Influenza viruses belong to the Orthomyxoviruses. They all range in severity but cause respiratory infection in the host animal.

There are several subtypes of the Influenza A virus. This virus is more commonly known as the "bird flu" in that infects mostly avian species although some have been found in mammals as well. These viruses range in the level of severity. H5N8 is one of the many subtypes. One of the main reasons for concern when it comes to these viruses is that they undergo constant change. This makes vaccine manufacturing almost impossible. By the time a vaccine is distributed, the virus may have already mutated. Although H5N8 is considered one of the lower pathenogenic subtypes, it is beginning to make a name for itself. Many times H5N8 is used as an incubator for the highly pathogenic H1N1.

H and N Designation

The types of viruses are designated by molecules found on the virus. The H for the type of hemaglutanin (the substance that allows the virus to bind to a specific cell).Hemagglutinin (influenza) is a glycoprotein that attaches the virus to the host cell (agglutinate.) There are many different types of H antigens. Each of these is specific to the subtype of the virus to which it belongs.

They are designated with the N for the enzyme neuraminidase (the substance that allows them to exit the cell and spread the virus.) As with hemaglutin, there are several types of neuraminidase that is specific to influenza. These are most frequently found in fowl.

Antigenic Shift Versus Antigenic Drift

One of the main reasons that any Influenza A virus is so deadly is because of antigenic shift. If a host cell is infected by two different viruses at the same time, the viruses can rearrange their RNA to produce a new strain. These new strains will be completely different from either of the parent cells. This will bypass any immunity that the host has built up to the original virus.

Antigenic drift are the less significant changes that happen to a virus over time. This is why one flu vaccine does not prevent all cases of the flu and also why you may get the flu more than once per season. At times, antigenic drift is the cause of a last minute scramble for a flu vaccine. Pharmaceutical companies may have a vaccine ready to be distributed but find that the particular strain is not the one that is cause for alarm that particular year.

Symptoms

For the most part symptoms of the H5N8 virus are respiratory. There are the common "flu-like" symptoms of fever, chills, headache, coughing and weakness. There are reports of there being conjunctivitis associated with the virus as well. When farmed poultry is suspected of having the virus and tests confirm, the farm will cull the birds. This way, the virus will hopefully not be passed along to the public. However, neighboring farms and area wildlife have to be tested as well.

Outbreaks

Perhaps the most known outbreak of H5N8 was in Ireland in 1983. Poultry on two farms showed the usual symptoms plus those of diarrhea, nervousness and depression. Poultry farms within close proximity began showing signs of the virus as well, although no contact could be established between the farms. In the end 8,000 turkeys, 28,020 chickens and 270,000 ducks were slaughtered. When investigated in the lab, clinical findings demonstrated that turkeys were the most susceptable to the virus. The virus could not be clinically reproduced in ducks.

There have been several pandemics involving other flu strains over the last century. After World War I, soldiers brought back the "Spanish Flu" from Europe. This virus was responsible killing hundreds of thousands around the world. In the late 1950s, the "Asian Flu" was brought into the US on naval ships. There were widespread deaths with this virus but it did give the opportunity for the spread of viruses to be studied more closely. Within the last 20 years, H5N1 (Avian Influenza Virus) has made an impact in Asia. This is a large concern for this country due to the fact that there is close contact with fowl in day-to-day activities. However, there have been a few cases in which this virus underwent human to human transmission. If human to human transmission became commonplace among any virulent avian virus, the results could be disastrous.

Famous quotes containing the word virus:

    If I knew for a certainty that a man was coming to my house with the conscious design of doing me good, I should run for my life ... for fear that I should get some of his good done to me,—some of its virus mingled with my blood.
    Henry David Thoreau (1817–1862)