Influenza Essay ⋆ Environment Essay Examples ⋆ EssayEmpire

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Inf luenza is an extremely contagious disease caused by the influenza virus. It causes infection of the respiratory tract and can affect millions of people every year. There are three types of influenza viruses. The influenza type A virus can infect humans and other animals, while influenza B and C viruses can only infect humans. Type A is responsible for the annual outbreak of influenza; the virus was first detected by a British bacteriologist Wilson Smith in 1932. Effects of the influenza virus C are very mild and do not cause epidemics. Influenza viruses are constantly changing, producing subtypes or strains. These strains are different from the main viruses, but retain some of their characteristics. These influenza strains may vary year to year, requiring flu vaccine modification every year.

In the Northern hemisphere, influenza epidemicity occurs during October-March. With the warming trends, the episode dies down. It surfaces in the tropics in March and April and during their rainy season. In May and August, the influenza episode moves to the southern hemisphere. By September, the episode comes back to the tropics. This annual cycle of influenza persists, and is different from measles, vermicelli, mumps, rubella, infestus, hepatitis, and smallpox.

Influenza usually is much more severe than the common cold. The virus takes about 1-2 days from the time of exposure to develop symptoms. This period is known as “incubation period.” The influenza (flu) comes on suddenly, causing symptoms such as fever, often as high as 104 degrees F, severe sweating, body and muscle aches, headache, fatigue, loss of appetite, dry cough, nasal congestion, and sore throat. The illness lasts up to 1-2 weeks, although fever generally lasts only 3-8 days. Most people recover without problem, but sometimes the ailment can lead to a bacterial infection such as bronchitis and ear/sinus infection.

One of the most severe complications of flu is bacterial pneumonia caused by streptococcus pneumoniae (the pneumococcus) and staphylococcus awieus. Pneumonia caused by flu is not common, but requires immediate hospitalization. Each year about 10,000-40,000 Americans die of influenza or influenza-related pneumonia, and over 90 percent of deaths occur in the 64+ age group. Influenza can be prevented by getting immunized with an influenza vaccine each year in the months of October and November. FluMist, a live virus vaccine in the form of nasal spray, can be an alternative to flu vaccine for healthy children and adults between the ages of 5-49, excluding pregnant women.

Scientists are actively looking for new drugs to prevent or treat flu. Two drugs such as Nimantadine and Amantadine have been in use for a number of decades. They are only effective against influenza type A and not type B. These drugs stop the flu from producing copies of itself once it has invaded the human cells. Zanamivin (trade name Relenza) and Oseltamivir (trade name Tamiflu) are the most recently discovered drugs, and are used to treat both flu types A and B.

Bird flu (avian influenza) is caused by complex flu viruses with a number of subtypes and strains. These viruses are classified as having high to low chance of causing disease. Scientists do not yet know just how these subtypes affect humans, but highly pathogenic viruses cause serious problems with a large number of deaths occuring both in animals and humans.

The virus does not infect people easily, and it almost never spreads to other humans. Bird Flu is mostly an avian disease. It has infected tens of millions of birds, but fewer than 200 people; and almost all of then caught it from birds. When a very nasty bird flu virus, A(H5N1) infects people, it can kill young people, devouring their lungs. The 2005 bird flu virus, A(H5 N1), has been steadily advancing from China to other parts of Asia, then to Europe and Africa. The latest country to report human cases is Azerbaijan, where out of seven people infected, five have died.

Bibliography:

John Barry, The Great Influenza: The Epic History of the Deadliest Plague in History (Viking, 2004);
Edgar Hope-Simpson, The Transmission of Epidemic Influenza (Plenum Press, 1992);
Remco S. Schrijver and Koch, Avian Influenza: Prevention and Control (Springer-Verlag, 2005).