Avian influenza is caused by highly species-specific influenza type A viruses that ordinarily infect only birds, and less commonly pigs. Migratory birds are the main reservoir of these viruses, though domestic birds are susceptible to the severe and fatal disease. From 1997, when an avian influenza virus was first documented to have passed from poultry to humans, to 19 January 2006, a total of 169 patients were confirmed to have acquired avian influenza during epidemics of highly pathogenic strains in poultry in Vietnam, Thailand, Hong Kong, Indonesia, China, Cambodia, and more recently Turkey, and of these 87 patients have died. Since 2003, the H5N1 type has been the most dominant and feared strain. The mortality rate of avian influenza virus infection in humans has been extraordinarily high (approximately 50%) compared to human influenza (<0.1%). Many other Asian countries have experienced epidemics of avian influenza with no reported cases in humans. The resulting economic losses have been in excess of US Dollars10 billion in Asia alone. Africa, a winter stopping place or residence for numerous species of migratory birds, might be the next continent to experience outbreaks. The Middle East, too, is located along the migratory routes of wild waterfowl. Therefore, these viruses may also spread to the Middle Eastern countries. The spread of the highly pathogenic avian influenza viruses can also occur through the importation of live poultry or movement of contaminated vehicles, cages, and other inanimate objects across countries.
Even though transmission of the avian influenza viruses to humans remains very limited, there are several reasons for concern. First, as with other influenza type A viruses, avian influenza viruses may undergo antigenic shift as a result of reassortment of genetic material with human influenza viruses during co-infection with both viruses in pigs or humans leading to a new human influenza virus that may then cause a major pandemic with a high mortality rate in humans. Second, there is as yet no commercially available human vaccine to prevent avian influenza infection. Third, there is a huge worldwide shortage of oseltamavir, an antiviral agent that can be used to treat and prevent avian influenza following exposure to infected birds, humans, or laboratory specimens containing the virus. Fourth, it will take several months to develop a human influenza vaccine against a new pandemic virus, should it emerge. This time lag will allow a global spread of the virus. The world is thus dealing with an unusually complex problem under pressure from a threat that could worsen rapidly and dramatically, in unpredictable ways.
The World Health Organization has urged all countries to develop plans in preparation for a pandemic. In Saudi Arabia, preparedness plans have been developed by the Ministry of Health (MOH), Ministry of Agriculture (MOA), Ministry of Commerce (MOC), and the National Commission for Wildlife Conservation and Development (NCWCD). The first line of defence is to prevent the introduction of the highly pathogenic H5N1 virus strain into the poultry population in Saudi Arabia and to immediately control and prevent the spread of any outbreak in birds as soon as it occurs. Consequently, the MOA has prohibited the importation of live birds from countries where avian influenza epidemics have occurred. Educational activities for workers on poultry farms have been intensified. A 24-hour toll-free telephone number (01-4030911) has been assigned by MOA to receive reports of diseases or deaths of poultry in the country. The MOA veterinary laboratories have also been equipped with the required diagnostic tests from poultry specimens. A preparedness plan to deal with any outbreak in birds has also been developed by the MOA and distributed to birds-producing projects. The MOC has prohibited the importation of frozen or chilled poultry meat from affected countries. The NCWCD has identified four locations in Saudi Arabia where migratory birds may land on-route to their final destinations. In collaboration with the MOA, samples from these birds are being regularly collected and tested for the presence of H5N1 strain. The MOH has circulated information on the disease, with a case definition for suspected and confirmed cases of avian influenza in humans and the required preventive and therapeutic interventions. In addition, enough oseltamavir doses to treat 800,000 patients have been purchased from the manufacturing company. Primers to detect H5N1 influenza virus strain by the polymerase chain reaction (PCR) technology from human respiratory specimens have been made available in the provincial laboratories in Riyadh, Jeddah, and Dammam. The MOH has also developed a preparedness plan to combat any avian or human influenza outbreaks in the country with special attention to the Hajj season. A committee of consultants in clinical infectious diseases has been assigned the active surveillance for avian influenza infection among pilgrims coming from affected countries.
It is believed that despite the global awareness of the importance to prevent the spread of highly pathogenic avian influenza and the emergence of a new human influenza virus capable of causing a new human influenza pandemic, most countries particularly the underdeveloped ones are ill-prepared because of limited resources. Therefore, it is perhaps more realistic to believe that a human influenza pandemic is inevitable in the foreseeable future and that the question is not “whether” but rather “when” a human influenza pandemic will occur.