Transmission and infection of H5N1 from infected avian sources to humans has been a concern since the first documented case of human infection in 1997, due to the global spread of H5N1 that constitutes a pandemic threat. Infected birds pass on H5N1 through their saliva, nasal secretions, and feces. Other birds may pick up the virus through direct contact with these excretions or when they have contact with surfaces contaminated with this material. Because migratory birds are among the carriers of the H5N1 virus it may spread to all parts of the world. Past outbreaks of avian flu have often originated in crowded conditions in southeast and east Asia, where humans, pigs, and poultry live in close quarters. In these conditions a virus is more likely to mutate into a form that more easily infects humans. A few isolated cases of suspected human to human transmission exist, with the latest such case in June 2006 (among members of a family in Sumatra). No pandemic strain of H5N1 has yet been found.
H5N1 vaccines for chickens exist and are sometimes used, although there are many difficulties, and it's difficult to decide whether it helps more or hurts more. H5N1 pre-pandemic vaccines exist in quantities sufficient to inoculate a few million people and might be useful for priming to "boost the immune response to a different H5N1 vaccine tailor-made years later to thwart an emerging pandemic". H5N1 pandemic vaccines and technologies to rapidly create them are in the H5N1 clinical trials stage but can not be verified as useful until after there exists a pandemic strain.
Environmental survival Avian flu virus can last indefinitely at a temperature dozens of degrees below freezing, as is found in the northernmost areas that migratory birds frequent. Heat kills H5N1 (i.e. inactivates the virus). Influenza A viruses can survive:
Over 30 days at 0 °C (32.0 °F) (over one month at freezing temperature) 6 days at 37 °C (98.6 °F) (one week at human body temperature) decades in permanently frozen lakes on hard non-porous surface such as plastic or stainless steel for 24–48 hours on clothes, paper and tissues for 8–12 hours While cooking poultry to 70 °C (158 °F) kills the H5N1 virus, it is recommended to cook meat to 74 °C (165 °F) to kill all foodborne pathogens. Inactivation of the virus also occurs under the following conditions:
30 minutes 60 °C (140.0 °F) (half-hour at a temperature that causes first and second degree burns in humans in ten seconds) Acidic pH conditions Presence of anti-microbial surfactants such as sodium dodecyl sulfate and lipid solvents Exposure to disinfectants: B-propiolactone, formalin, and iodine compounds Ordinary levels of chlorine in tap water kill H5N1 in public water systems.
To kill avian flu viruses, (the) World Health Organization recommends that environmental surfaces be cleaned by the following: Disinfectants such as sodium hypochlorite, 1% in-use dilution, 5% solution to be diluted 1:5 in clean water, for materials contaminated with blood and body fluids Bleaching powder seven grams per liter with 70% available chlorine for toilets and bathrooms 70% alcohol for smooth surfaces, tabletops, and other surfaces where bleach cannot be used H5N1 "can remain infectious in municipal landfills for almost 2 years. [...] The two factors that most reduced influenza survival times were elevated temperature and acidic or alkaline pH."
Avian flu in birds
According to Avian Influenza by Timm C. Harder and Ortrud Werner:
Following an incubation period of usually a few days (but rarely up to 21 days), depending upon the characteristics of the isolate, the dose of inoculum, the species, and age of the bird, the clinical presentation of avian influenza in birds is variable and symptoms are fairly unspecific. Therefore, a diagnosis solely based on the clinical presentation is impossible. The symptoms following infection with low pathogenic AIV may be as discrete as ruffled feathers, transient reductions in egg production or weight loss combined with a slight respiratory disease. Some LP strains such as certain Asian H9N2 lineages, adapted to efficient replication in poultry, may cause more prominent signs and also significant mortality. In its highly pathogenic form, the illness in chickens and turkeys is characterised by a sudden onset of severe symptoms and a mortality that can approach 100% within 48 hours. The current method of prevention in animal populations is to destroy infected animals, as well as animals suspected of being infected. In southeast Asia, millions of domestic birds have been slaughtered to prevent the spread of the virus.
Poultry farming practices There have been a number of farming practices that have changed in response to outbreaks of the H5N1 virus, including:
vaccinating poultry against bird flu vaccinating poultry workers against human flu limiting travel in areas where H5N1 is found increasing farm hygiene reducing contact between livestock and wild birds reducing open-air wet markets limiting workers contact with cock fighting reducing purchases of live fowl improving veterinary vaccine availability and cost. For example, after nearly two years of using mainly culling to control the virus, the Vietnamese government in 2005 adopted a combination of mass poultry vaccination, disinfecting, culling, information campaigns and bans on live poultry in cities.
Dealing with outbreaks The majority of H5N1 flu cases have been reported in southeast and east Asia. Once an outbreak is detected, local authorities often order a mass slaughter of birds or animals infected or suspected to be infected.
Use of vaccines Dr. Robert G. Webster et al. write
… excerpt ends here. Continue reading the full article.
