Flu or influenza is an infectious disease caused by a type of RNA virus. Influenza viruses are characterized by a strong genetic variability, being classified in types A, B and C. A high mutation frequency leads to modifications in the glycoproteins, responsible of the typical pandemias and endemias of Influenza A and B viruses. The ability to exchange genetic information between human and animal viruses of Influenza A leads to the generation of new subtypes like H5N1 or H1N1.
Clinical Characteristics: in human beings affects to the respiratory tract and the virus spreads easily from person to person. The infection usually lasts for one week and it is characterized by of high fever, muscle ache, headache, sore throat and cough.
Incidence: influenza virus infections are globally spread in the northern hemisphere between October and March, while in the southern hemisphere is affected between May and September. Incubation period is from 1 to 3 days, and most people recover in one or two weeks without receiving medical treatment. However, the infection in children, elderly patients and people with other serious medical affections can imply serious complications of the underlying illness, causing pneumonia or even death.
Diagnostic Methods: Isolated cases out of the epidemic season are difficult to diagnose clinically. It is also difficult to reach a clinical diagnosis during epidemics, since it can be confused with other respiratory diseases. Hence, the laboratory diagnosis is highly useful, particularly in high risk patients. Complement fixation, ELISA and IFA are the most useful serological techniques to diagnosis the disease, although most cases are diagnosed by molecular biology, cell culture and antigen detection techniques.