Mammals and birds harbor flu viruses; avian strains typically are passed from aquatic birds or ducks to chickens or pigs, which are intermediate hosts. People then pass human influenza to these hosts, where the viruses combine to produce a new pathogen. Most flu outbreaks are mild and self-limiting. People with asthma, diabetes, kidney disease or compromised immune systems tend to be the most vulnerable.
Symptoms
Sudden onset, high fever and muscle aches can indicate something more serious than a cold is challenging the immune system. Children may have stomach upset. By day three, fever typically breaks but cold-like symptoms of cough, sore throat, congestion, headache, and runny nose remain. The flu drains energy; most victims are in bed for up to seven days and fatigue can linger another ten days.
Transmission
Droplets spread influenza rapidly; the virus has an incubation period of one or two days. Moist, pathogen-loaded particles are exhaled, coughed and sneezed to be inhaled by new victims or spread by contaminated items. People recovering from the flu should not to leave home until they have been free of fever for at least 24 hours. Hand washing is effective against the spread of viruses.
Types
The most common and worst type, influenza A, creates seasonal epidemics and has subtypes capable of causing pandemics. Influenza B can also cause seasonal epidemics but has no subtypes. Type C produces mild symptoms and is not thought to cause epidemics, according to the Centers for Disease Control and Prevention (CDC). Seasonal flu outbreaks in the United States generally occur between December and March and most often peak in January.
History
Epidemics and pandemics both surpass efforts to control the spread of disease. The difference lies in the number of deaths and areas involved. A pandemic generally is a global epidemic.The Spanish flu pandemic of 1918 claimed the lives of 50 million people, according to the CDC.
Flu virus was isolated in 1933, and vaccines were developed in response to the 1957 Asian flu pandemic, which claimed about two million lives. Asian flu disappeared in 1968, replaced by the Hong Kong flu pandemic, which killed 700,000 people.
Avian flu made headlines in 1997 because it is capable of moving directly from birds to humans. This turned out to be a rare occurrence, but the Monterey Institute of International Studies continues to monitor effects of the virus on fowl in Southeast Asia.
Swine flu, or H1N1, became pandemic in 2009. The disease did not follow the usual pattern of seasonal flu outbreaks and peaked in October, according to the CDC.
Prevention/Solution
The CDC recommends that everyone, except those with severe allergy to eggs or a history of Guillain-Barre Syndrome, be vaccinated against the flu. The emergence of new strains is unpredictable, but combination vaccines can provide some protection against genetically similar strains even if the vaccine is not a perfect match for circulating viruses.
