Return of Avian Influenza: What Is the Core of the Problem?
10.2185/jjrm.53.775
- VernacularTitle:鳥インフルエンザの流行は，何が問題なのか
- Author:
Harue OKADA
;
Mahito TASHIRO
- Publication Type:Journal Article
- From:Journal of the Japanese Association of Rural Medicine
2004;53(5):775-782
- CountryJapan
- Language:Japanese
-
Abstract:
In January and February 2004, avian influenza assaulted poultry farms in Yamaguchi Prefecture and in Kyoto Prefecture, killing a large number of chickens and sparking a wholesale slaughter of birds near the affected areas. To prevent the spread of the flu, authorities banned the shipment of live chickens, eggs and poultry meat within a radius of 30 kilometers around the infected poultry farms. Even now, you may be able to picture to yourself that masked workers, wearing white work clothes, goggles, boots and gloves, were burying flocks of dead chickens deep in the ground and sanitizing the facilities through and through. Japanese mass media gave prominent coverage to the bird flu outbreaks in terms of food safety, and with good reason. Chicken eggs and meat are in great demand and constitute important items in Japanese dietary culture and habits.
Vaccines for a human strain of influenza virus are made every year by using chicken eggs to grow a master-seed virus. To ensure a stable supply of human flu vaccines, the epidemic of bird flu must be blocked by all means.
After all is said and done, the crux of the problem is the ability of the avian flu virus. It can mutate, cross with another flu virus to form a new type of influenza virus that is transmissible from humans to humans, thus causing a global pandemic. As you must have heard, those influenza viruses which caused Spanish flu, Asian flu and Hong Kong flu were derived from an avian flu virus. The virus mutated into new forms of human flu virus and invaded the domain of humans, claiming millions of human lives and triggering crises worldwide. These new forms of human influenza occur in a 27-year cycle. The previous occurrence of a new type of influenza was Hong Kong flu of 1968.
There is every indication that bird flu, which has the potential to pass easily among humans, is spreading in Asia. Since the spring of 2004, the return of bird flu has become apparent in Thailand and Vietnam where the epidemic was declared to be under control. Even some human cases of avian influenza have been reported. The mortality rate from avian flu is very high. It is estimated that 70% of the patients with bird flu die. The currently prevalent strain of bird flu virus is regarded as a remarkably lethal pathogen. Being so virulent, it attacks chickens systemically and kills them in one or two days. There is general agreement among flu virus experts that the pathogen, known as the H5N1 virus, will sooner or later break the species barrier and begin affecting the human population.
Such being the circumstances, we shall deal with the incidence of avian influenza in this paper and ponder over what constitutes the core of the problem, how a new strain comes along from the avian influenza virus and what is expected to happen when a new strain of flu virus emerges. By gaining an insight into a new type of influenza and taking lessons from past pandemics that took a heavy toll of human lives, we should make every effort to arrest the spread of the disease and keep the damage to a minimum.
