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Print ArticleScientists have discovered how bird flu adapts in patients, offering a new way to monitor the disease and prevent a pandemic, according to research published in the August issue of the Journal of General Virology. Highly pathogenic H5N1 avian influenza virus has spread through at least 45 countries in 3 continents. Despite its ability to spread, it cannot be transmitted efficiently from human to human. This indicates it is not fully adapted to its new host species, the human. However, this new research reveals mutations in the virus that may result in a pandemic.
"The mutations needed for the emergence of a potential pandemic virus are likely to originate and be selected within infected human tissues," said Professor Dr Prasert Auewarakul from Mahidol University, Thailand. "We analyzed specific molecules called haemagglutinin on viruses derived from fatal human cases. Our results suggest new candidate mutations that may allow bird flu to adapt to humans."
Viruses with a high mutation rate such as influenza virus usually exist as a swarm of variants, each slightly different from the others. These are called H5N1 bird flu quasispecies. Professor Dr Auewarakul and his colleagues found that some mutations in the quasispecies were more frequent than others, which indicates they may be adaptive changes that make the virus more efficient at infecting humans. Most of these mutations were found in the area required for the virus to bind to the host cell.
"This study shows that the H5N1 virus is adapting each time it infects a human," said Professor Dr Auewarakul. "Such adaptations may lead to the emergence of a virus that can cause a pandemic. Our research highlights the need to control infection and transmission to humans to prevent further adaptations."
The research has provided genetic markers to help scientists monitor bird flu viruses with pandemic potential. This means they will be able to detect potentially dangerous strains and prevent a pandemic. The research also gives new insights into the mechanism of the genesis of a pandemic strain.
"Our approach could be used to screen for mutations with significant functional impact," said Professor Dr Auewarakul. "It is a new method of searching for changes in H5N1 viruses that are required for the emergence of a pandemic virus. We hope it will help us to prevent a pandemic in the future."
Source : Society for General Microbiology
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CUT THE CHAIN OF INFECTIONS !
Spread of avian flu by drinking water:
Proved awareness to ecology and transmission is necessary to understand the spread of avian flu. For this it is insufficient exclusive to test samples from wild birds, poultry and humans for avian flu viruses. Samples from the known abiotic vehicles as water also have to be analysed. Proving viruses in water is difficult because of dilution. If you find no viruses you can not be sure that there are not any. On the other hand in water viruses remain viable for a long time. Water has to be tested for influenza viruses by cell culture and in particular by the more sensitive molecular biology method PCR.
Transmission of avian flu by direct contact to infected poultry is an unproved assumption from the WHO. There is no evidence that influenza primarily is transmitted by saliva droplets: “Transmission of influenza A in human beings” http://www.thelancet.com/journals/laninf/article/PIIS1473309907700294/abstract?iseop=true.
There are clear links between the cold, rainy seasons as well as floods and the spread of influenza. There are clear links between avian flu and water, e.g. in Egypt to the Nile delta or in Indonesia to residential districts of less prosperous humans with backyard flocks of birds and without a central water supply as in Vietnam: http://www.cdc.gov/ncidod/EID/vol12no12/06-0829.htm. See also the WHO web side: http://www.who.int/water_sanitation_health/emerging/h5n1background.pdf. That is just why abiotic vehicles as water have to be analysed. The direct biotic transmission from birds, poultry or humans to humans can not depend on the cold, rainy seasons or floods. Water is a very efficient abiotic vehicle for the spread of viruses - in particular of fecal as well as by mouth, nose and eyes excreted viruses. Infected humans, mammals, birds and poultry can contaminate drinking water everywhere. All humans have very intensive contact to drinking water. Spread of avian flu by drinking water can explain small clusters in households too.
Avian flu infections may increase in consequence to increase of virus circulation. Human to human and contact transmission of influenza occur - but are overvalued immense. In the course of influenza epidemics in Germany, recognized clusters are rare, accounting for just 9 percent of cases e.g. in the 2005 season. In temperate climates the lethal H5N1 virus will be transferred to humans via cold drinking water, as with the birds in February and March 2006, strong seasonal at the time when (drinking) water has its temperature minimum.
The performance to eliminate viruses from the drinking water processing plants regularly does not meet the requirements of the WHO and the USA/USEPA. Conventional disinfection procedures are poor, because microorganisms in the water are not in suspension, but embedded in particles. Even ground water used for drinking water is not free from viruses.
In temperate regions influenza epidemics recur with marked seasonality around the end of winter, in the northern as well as in the southern hemisphere. Although seasonality is one of the most familiar features of influenza, it is also one of the least understood. Indoor crowding during cold weather, seasonal fluctuations in host immune responses, and environmental factors, including relative humidity, temperature, and UV radiation have all been suggested to account for this phenomenon, but none of these hypotheses has been tested directly. Influenza causes significant morbidity in tropical regions; however, in contrast to the situation in temperate zones, influenza in the tropics is not strongly associated with a certain season.
In the tropics, flood-related influenza is typical after extreme weather. The virulence of influenza viruses depends on temperature and time. Especially in cases of local water supplies with “young” and fresh influenza-contaminated water from low local wells, cisterns, tanks, rain barrels, ponds, rivers or rice paddies, this pathway can explain H5N1 infections. At 24°C, for example, in the tropics the virulence of influenza viruses in water exists for 2 days. In temperate climates with “older” water from central water supplies, the temperature of the water is decisive for the virulence of viruses. At 7°C the virulence of influenza viruses in water extends to 14 days.
Ducks and rice (paddies = flooded by water) are major factors in outbreaks of avian flu, claims a UN agency: Ducks and rice fields may be a critical factor in spreading H5N1. Ducks, rice (fields, paddies = flooded by water; farmers at work drink the water from rice paddies) and people – not chickens – have emerged as the most significant factors in the spread of avian influenza in Thailand and Vietnam, according to a study carried out by a group of experts from the United Nations Food and Agriculture Organization (FAO) and associated research centres. See http://www.un.org/apps/news/story.asp?NewsID=26096&Cr=&Cr1
The study “Mapping H5N1 highly pathogenic avian influenza risk in Southeast Asia: ducks, rice and people” also concludes that these factors are probably behind persistent outbreaks in other countries such as Cambodia and Laos. This study examined a series of waves of H5N1, a highly pathogenic avian influenza, in Thailand and Vietnam between early 2004 and late 2005. Through the use of satellite mapping, researchers looked at several different factors, including the numbers of ducks, geese and chickens, human population size, rice cultivation and geography, and found a strong link between duck grazing patterns and rice cropping intensity.
In Thailand, for example, the proportion of young ducks in flocks was found to peak in September-October; these rapidly growing young ducks can therefore benefit from the peak of the rice harvest in November-December, at the beginning of the cold: Thailand, Vietnam, Cambodia, Laos – as opposed to Indonesia – are located in the northern hemisphere.
These peaks in the congregation of ducks indicate periods in which there is an increase in the chances for virus release and exposure, and rice paddies often become a temporary habitat for wild bird species. In addition, with virus persistence becoming increasingly confined to areas with intensive rice-duck agriculture in eastern and south-eastern Asia, the evolution of the H5N1 virus may become easier to predict.
Dipl.-Ing. Wilfried Soddemann - Epidemiologist - Free Science Journalist soddemann-aachen@t-online.de http://www.dugi-ev.de/information.html
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