Influenza is an infectious disease caused by the influenza virus that affects birds and mammals, including man.
Influenza virus belonging to the family Orthomyxoviridae. There are different kinds or types, the most important are the A, B and C. Are distinguished by the characteristics of their antigens (proteins that provoke an immune response). The largest outbreaks of influenza have been caused mainly by the type A.Type A has a protein or antigen on their surface (H and N) which change each year and consequently population exists without immunity to the virus and therefore susceptible to infection.
Influenza epidemics occur in the winter months in temperate areas of the world: being October and March in the northern hemisphere, and between April and September in the southern hemisphere.
Epidemics occur regularly end up affecting the entire planet, are what are called pandemics. They are usually caused by type A. In the twentieth century there were 5 pandemics, including 1918-19 (the so-called Spanish flu), with over 50 million deaths, and the last in 1977 (known as the Russian flu).
The flu virus is spread through respiratory droplets or saliva laden with viruses that spread by coughing or sneezing, but also deposited in the hands or inert surfaces.
Influenza has an incubation period of one to three days. The infection affects the respiratory system.
Influenza epidemics begin abruptly, reach a maximum in 2-3 weeks, last two to three months and disappear almost as quickly as they appeared. In epidemics usually occurs between 10 and 20% of the population.
The mortality from influenza occurs in people with risk factors, the main heart disease or chronic respiratory and older. Diabetes and pregnancy (especially the second and third quarters) are also risk factors for influenza and its complications.
The flu begins abruptly with symptoms such as fever, headache, muscle or joint pain, weakness and general discomfort. Within days, is accompanied by respiratory symptoms (cough and sore throat). The cough is usually dry and can last several days or weeks. Unlike simple colds, the flu can last from one to two weeks until full recovery, but the normal average is about 5 days.
The main complication is pneumonia, which can be fatal. Pneumonia or lung infection is accompanied by fever and shortness of breath (dyspnea). It can be caused by the virus itself or as a super infection of the lung by bacteria.
Another cause of mortality in people is affected by the imbalance of the underlying diseases, whether cardiac or respiratory.
In most cases, the diagnosis is clinical, ie based on the presence of typical symptoms of influenza in the context of an epidemic.
Laboratory diagnosis is cost quite expensive: is achieved by isolating the virus in throat swab, sputum or nasopharynx, but carries a week to get the results. Another faster, which only takes a few hours, is to detect viral proteins in the samples.
In uncomplicated influenza, which is the usual symptoms are treated: for fever antipyretics, analgesics for pain and cough medicines if it really is very annoying. It is important to rest and hydrate home when there is high fever.
Drugs that act specifically against the virus, antivirals, are indicated only in severe cases or in patients at risk and always under medical prescription. Get Antivirals shorten illness if they begin to manage it early.
On one hand it can attempt to prevent contagion taking hygienic measures during outbreaks of influenza:
On the other hand there are vaccines. Vaccines with inactivated (“dead”) or attenuated virus. Each year in the fall, before epidemics, vaccination is recommended for people at risk: over 65 years, patients with significant underlying diseases and health personnel. Because the virus varies from year to year, the vaccine is designed depending on the type of virus circulating latest and for this reason should be administered every year.