Реферат: Influenza Virus Essay Research Paper I N
Influenza Virus Essay, Research Paper
I N F L U E N Z A V I R U S
Influenza virus is something most people get at least once in their lifetime. It is commonly known as the flu. It contains single stranded RNA. It attacks both human and animals. It reproduces in a lytic cycle. It is inhaled and comes in contact with cells of the upper air passage. It penetrates the cells that line these passages and reproduce. New viruses are released from the infected cells and infect other cells along the respiratory tract. It could also be carried away in exhaled air and infect other people. Influenza by itself is not usually a serious disease. But it can lower the body s resistance, and leads to bronchitis and pneumonia especially for elder, innutrition, and people with lung or heart problems.
The flu virus was first isolated from chickens in 1901, but it was recognized as so until 1955. The flu virus was also isolated from runny pig snouts in 1931. This virus became know as “swine flu.” There are three main types of influenza simply named A, B, C. Influenza A is the most common was discovered in 1933. Influenza B was discovered in 1940 and influenza C in 1947. Variants of these basic types are named after the place it first strikes. For example, there is the Hong Kong (B), New Jersey (A), and Bangkok (A). Symptoms of the virus include a sore throat, fever, fatigue, coughing, aches, and loss of appetite.
Influenza not only affects humans but they also infect other animals such as pigs and turkey. Not only that, but it easily crosses species. Thus, new viruses are probably created in pigs and waterfowl, like ducks and seagulls, and then later passed on to other creatures. For example, in 1980, the virus produced an epidemic in seals and caused conjunctivitis in humans who tried to help.
The influenza virus can also last for hours in dried mucus. Viruses are usually roughly spherical and about 200nm in diameter. The envelope contains rigid “spikes” of haemagglutinin and neuraminidase, which form a characteristic halo of projections around negatively stained virus particles.
The virus has tons of genetic material protected by a sphere surrounded by layers of fat and protein. All this genetic material is like having hundreds of pieces of legos, which you can make tons of different shapes with. Thus, it mutates easily and frequently. This means you’ll probably never be immune from the flu.
Influenza epidemics are probably as old as human history. It is hard to trace its path because of its genetic symptoms. It probably plagued Athens in 430 B.C. and destroyed Charlemagne’s army in 876 A.D. There is also strong evidence of an outbreak in the sixteenth century too. The first recorded pandemic was in 1580 across Africa and Europe. It killed thousands in 1647 as it moved from the Caribbean to New England. It is often known by names such as “la grippe,” “jolly rant,” or “the new acquaintance.” It was after the epidemic of 1732-33 in the American colonies that an English doctor named John Huxham introduced an old Italian folk term, which connected the colds, cough, fevers to the astrological “influence” of the stars. Thus came the popularity of the term influenza.
However, it never really attracted much attention in history as other diseases. That is until the epidemic of the “Spanish flu” in 1918-19. This epidemic is 20th century’s worst and deadliest disease faced by any modern western society. The epidemic seemed to have started in the U.S. By estimates, 21 million people died worldwide out of a billion infected. At least 12 million died in India. There were about 550,000 deaths in the U.S. Inuit villages in Alaska were wiped out. However, no blood samples were saved from this epidemic so it will never be known exactly what type of virus caused this epidemic. Epidemics like this could happen again. Influenza viruses such as the Hong Kong flu, which killed about 70,000 people in the U.S. in 1968-9, remind us that influenza should not be completely ignored.
There are no drugs that can cure influenza and no reasonable way to avoid it. The only treatment for influenza is bed rest. Medicine can control the fever and reduce the pain. The vaccine is really the only defense. However, since there are so many variations of this virus, a vaccine each year is really a guess as to the most common virus to be seen that year. For example, the CDC studies 1,500 flu virus samples from 120 laboratories around the world. Then, in March 1994 they decide to make a vaccine from three strains: A-Texas, B-Panama, A-Shangdong. Seventy million doses are manufactured for use that fall. Immunity develops one to two weeks after the shots.
The vaccine is made from dead viruses so people can’t get the flu from a flu shot. However, people allergic to eggs should avoid the vaccine since they are grown in chicken eggs. The vaccine can reduce the rate of occurrence in people over 60 by half. If people do get the flu even though they’re vaccinated, they usually experience milder symptoms.