Influenza viruses are highly species-specific. This means that viruses that infect an individual species (humans, certain species of birds, pigs, horses, and seals) stay “true” to that species, and only rarely spill over to cause infection in other species. But the problem is that if the animal influenza virus still jump the species barrier and infect humans, the body is completely exposed and unadapted to such disease. In fact, it is a new virus that is unknown to our immune system, and thus is very dangerous. Infection is difficult, atypical and leads to many complications. In addition, modern medicine has virtually powerless to combat the flu.
In order to cause an epidemic among humans, the virus must not only “learn” to move from diseased poultry, but also from person to person. While the virus does not mutate and acquire the properties necessary for this avian influenza epidemic we are not afraid.
During the first documented outbreak of H5N1, which occurred in Hong Kong in 1997, 18 human cases coincided with an outbreak of highly pathogenic avian influenza, caused by a virtually identical virus, in poultry farms and live bird markets. Extensive studies of the human cases have been identified as the source of infection was the direct contact with diseased poultry. During the research conducted among family members and other individuals who have had contact with patients, as well as among health care workers who care for them, and the miners of birds, it was found that, if there was a transfer of the virus from person to person, it was very limited. Human infections ceased following the rapid (within three days), the destruction of entire poultry population in Hong Kong, estimated at around 1.5 million birds.
The symptoms of avian influenza
The clinical picture of avian influenza differ a great variability, and the disease is usually accompanied by severe respiratory failure and the development of viral pneumonia, which cause and severity of the disease.
The incubation period lasts from 2 to 8 days. Initial symptoms are similar to regular flu: muscle aches, runny nose, cough and sometimes diarrhea, vomiting, pain in the abdomen and chest and bleeding from the nose and gums. In patients infected with H5N1, there is a rapid clinical deterioration. The period between the onset of illness and the development of acute respiratory distress was around six days. In total, more than half of the laboratory-confirmed cases have been fatal.
What can a doctor?
In the arsenal of physicians has a number of antiviral drugs that have some therapeutic effect in early treatment. Otherwise, use the symptomatic treatment.
At present, H5N1 avian influenza remains largely a disease of birds. The species barrier is significant: the virus does not spread easily from birds to humans. Despite the infection since mid-2003 tens of millions of poultry over large geographical areas, fewer than 200 laboratory confirmed human cases.
Prevention of avian influenza
Of all the viruses that circulate in birds H5N1 flu virus poses the greatest danger to people. All evidence to date suggests that the main source of human infection is close contact with dead or sick birds and their droppings.