Influenza B: Description, Causes and Risk Factors:
Influenza caused by strains of influenza virus type B; outbreaks are usually more limited than those due to influenza virus type A, although infections by the two types are clinically indistinguishable; occasionally associated with Reye syndrome.
The Influenza B virus capsid is enveloped while its virion consists of an envelope, a matrix protein, a nucleoprotein complex, a nucleocapsid, and a polymerase complex. It is sometimes spherical and sometimes filamentous. It surface projections are made of hemagglutinin and neuraminidase.
Influenza B is a type of flu that is similar to influenza A. However, while A usually afflicts people in the early winter, influenza B can infect any time of the year. Another difference between the two is that type B can only pass from human-to-human, or seals, unlike type A bird flu or swine flu. Type A and B share many symptoms.
Influenza B is less common but still causes outbreaks of seasonal flu. One strain of influenza B is included in the seasonal flu vaccine every year to protect people from the strain that researchers believe is most likely to cause illness during the upcoming flu season.
Influenza B viruses are not divided into subtypes, but can be further broken down into different strains.
In nature, the flu virus is found in wild aquatic birds such as ducks and shore birds. It has persisted in these birds for millions of years and does not typically harm them. But the frequently mutating flu viruses can readily jump the species barrier from wild birds to domesticated ducks and then to chickens. From there, the next stop in the infectious chain is often pigs.
Pigs can be infected by both bird (avian) influenza and the form of influenza that infects humans. In a setting such as a farm where chickens, humans, and pigs live in close proximity, pigs act as an influenza virus mixing bowl. If a pig is infected with avian and human flu simultaneously, the two types of virus may exchange genes. Such a "re-assorted" flu virus can sometimes spread from pigs to people.
Depending on the precise assortment of bird-type flu proteins that make it into the human population, the flu may be more or less severe.
In 1997, for the first time, scientists found that bird influenza skipped the pig step and infected humans directly. Alarmed health officials feared a worldwide epidemic (a pandemic). But, fortunately, the virus could not pass between people and thus did not spark an epidemic. Scientists speculate that chickens may now also have the receptor used by human-type viruses.
The influenza B virus can live for weeks on surfaces like faucets and door handles. The best forms of prevention are washing hands before and after using a public restroom, wearing a face mask when in crowded public areas, refraining from sharing foods and beverages, and taking vitamin C to build a strong immune system.
Most people will experience symptoms such as coughing, fever, headache, body aches, exhaustion and congestion, nausea and vomiting. The symptoms come on strong and fast, not gradually. They typically last between 3 and 7 days and you feel so bad that it is hard to do almost anything other than lay in bed.
In otherwise healthy individuals who develop influenza during outbreaks, no tests are generally required to diagnose the illness. If there is thought to be a pandemic risk, testing may occur for public health purposes. If a person develops a severe respiratory infection, and influenza is one of the possible causes, testing may be carried out to make sure the correct treatment is given. Testing usually involves the doctor taking swabs from the back of the nose and back of the throat, which are then sent to the laboratory to identify whether influenza is present, and if so, what type.
If the doctor suspects you have developed pneumonia, further tests such as blood tests, sputum specimens, and chest x-rays may be required.
Several antiviral drugs and neuraminidase inhibitors (RelenzaSM
) are available that have both prophylactic and clinical efficacy, although resistance, including transmission of primary resistant strains, is a major concern.
Influenza virus is one of the most changeable of viruses. These genetic changes may be small and continuous or large and abrupt. Small, continuous changes happen in type A and type B influenza as the virus makes copies of itself. The process is called antigenic drift
. The drifting is frequent enough to make the new strain of virus often unrecognizable to the human immune system. For this reason, a new flu vaccine must be produced each year to combat that year's prevalent strains.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.