14 DAY TRIAL // Avian influenza is an infectious disease of birds which occurs worldwide. All birds are exposed to the infection, even if some wild birds which carry the virus do not show signs of infection.
The previous cases of the infection showed a great number of victims struck by various forms of the avian influenza. Of the hundreds of strains of avian influenza A viruses, only four are known to have caused human infections: H5N1, H7N3, H7N7, and H9N2.
In 1918, the Spanish Flu pandemic, caused by the H1N1 influenza virus, also an avian strain, killed an estimated 20 million to 50 million people worldwide. Over 400 million got infected in about 18 months. 675,000 Americans died of Spanish flu, of which 200,000 died in October of 1918 alone. The first pandemic spread alarmingly fast when the population was only a third of what it is today.
The H2N2 influenza followed in 1957, killing 100,000 people, after which, in 1968, the H3N2 influenza virus caused the death of 700,000 people. H2N2 and H3N2 are likely to have appeared after an exchange of genes between avian and human flu viruses.
The threat of bird flu diminished until the recent H5N1 virus was isolated for the first time in a human patient in Hong Kong in May 1997. 18 people were infected with the virus, after having close contact with the poultry, 6 of them dying. People have been infected from contact with live infected poultry, the virus jumping from birds to humans. Poultry in Hong Kong have been rapidly destroyed, about 1.5 million in 3 days' time, in order to stop the disease being transmitted to humans.
Birds that survive infection excrete virus for at least 10 days, orally and in feces, so further spread is a great risk at live poultry markets, and alsoby migratory birds. Symptoms of bird flu include, along fever of over 38 degrees Celsius, diarrhea, vomiting, abdominal pain, chest pain, nose or gum bleeding. Almost all patients develop pneumonia, which does not respond to antibiotics, and difficulty breathing or respiratory secretions containing blood.
The H5N1's profile is almost identical to the one from 1918, the only real defense being an immune response from the organism. But, as the virus mutates, the immune system does not longer recognize it and takes more time to produce a response.
Many vaccines have been created against bird flu, tested and some even put out on the market, one of the most familiar being Tamiflu. Tamiflu can reduce the duration of viral replication if it is administered within 48 hours after the symptoms onset. Even if the drug was conceived for the treatment and prophylaxis of seasonal influenza, it is recommended as soon as possible for cases of bird flu. The drugs are effective as long as the virus remains stable and enough time is given to produce vaccines.
Considering the mutation of the virus, vaccines against the new strains take more time to produce. At least 4 months would be needed to produce a new vaccine, in significant quantities, capable of conferring protection against a new virus subtype.
So far, nine Asian countries have reported the infection: the Republic of Korea, Vietnam, Japan, Thailand, Cambodia, the Lao People's Democratic Republic, Indonesia, China, and Malaysia, among which Japan, the Republic of Korea, and Malaysia have managed to isolate the disease and are now free of the virus. In July 2005, the virus spread to the Russian Federation, Kazakhstan and Mongolia. October 2005 was the month in which Turkey, Romania, and Croatia reported the infection, while in early December 2005 Ukraine reported its first outbreak in domestic birds.
Many countries were infected by migratory birds which carried the H5N1 virus. They carry it in its highly pathogenic form, over long distances. Before the death of 6 000 migratory birds in China in late April 2005, the virus could only be found within short distances of the outbreaks. Despite the infection of tens of millions of poultry over large geographical areas since the first infection in 2003, fewer than 200 human cases have been confirmed by laboratory tests.
To this date, human cases of bird flu infection have been reported in 6 countries, mostly African: Cambodia, China, Indonesia, Thailand, Turkey, and mostly Vietnam, with more than 90 cases. Even if more than half of the human cases were fatal, avian influenza in humans is still a rare disease.