INFLUENZA

Indroduction:

Influenza is an acute respiratory tract infection caused by the influenza virus, of which there are 3types- A,B,and C pandemic were caused by the influenza A strain due to various factors. The disease is characterized by sudden onset of chills,malaise, fever muscular pains and cough.

Problem statement:

Influenza is found all over the world. It occurs in all affectes million of people, outbreak of influenza A occur virtually every year. Major Epidemic occur at intervals of 2 of 3 years, and pandemic at intervals of 10-15 years. The Frist pandemic during the present century occurred in 1918-19, which affected an estimate 500 milon people and kiled more than 20 milon. In India alone, over six milon people died during this pandemic.

Epidemic Behaviour:

Influenza is truly an international disease. It occurs in all countries and affected millions of people every year. Its behaviour is unpredictable. It may occur in serval forms. It may smolder in a community without recognition, being manifest only by serological surveys. It may occur in pandemics every year 10 to 15 yeras due to major antigenic changes.

Mode of Transmission:

Influenza is spread mainly from person by droplet infection or droplet Nucleic created by sneezing, coughing or taking. The portal of entry of the virus is the respiratory tract.

Inclubation period:

The inclubation period is about 18 to 72 hours

Pathogenesis and clinical Features:

The virus enters the respiratory tract and causes inflammation and necrosis of superficial epithelium of the bronchial mucosa, followed by secondary bacterial invasion. There is viraemia. Both the viruses cause much the same symptoms, fever, chills, aches and pains, coughing and generalized weakness. Fever lasts from 1 to 5 days, averaging about 3 days in adults. The most dreaded complications is pneumonia, which should be suspected it fever persists beyond 4 or 5 days, or recurs abruptly after convalescence.

Agent factor

Agent:

Influenza virus are classified within the family of orthomyoxvirdae. There are threes viral subtypes, mainly type A,B and types C. These three viruses are viruses are antigenically distinct There is no cross immunity between them. Of importantnce are them. Of importantnce A and B virus which are responsible for epidemic of disease throughout the world.

The influenza A virus is unique  among the virus because it is frequently subject to antigenic variation, both and minor.

As of now, three of influenza virus A- (HIN1) ,A (H3N2) and B exist, influenza viruses of the H131 subtype have caused have caused of the disease in two period of this century – from about 1946 up until 1957, and from 1977 until the present.