Bird flu virus in the environment

There's a tremendous amount of influenza A/H5N1 ("bird flu" virus) all over southeast asia and other areas where the virus is endemic in poultry. Where is this virus, exactly? We know it's in the infected birds and in their respiratory secretions and feces. We know it occasionally infects mammals (including humans). Is it found in the environment? We know very little about this, although there is good evidence it is in water where aquatic birds like ducks spend time and likely one way the virus is spread from bird to bird. In lab experiments, the virus remains intact on inanimate surfaces for many days. What about in the "real world"? A paper just published in CDC's journal, Emerging Infectious Diseases, makes a small beginning to find out by examining mud, pond water, water plants, and soil swabs close to areas in Cambodia that have had infected backyard poultry.

From the paper:

In response to notification of a confirmed case of influenza subtype H5N1 infection in humans or poultry, we surveyed all households located within a 1-km radius of the outbreak site. We gathered data on proportion of deaths in poulty flocks and on interaction with other species by conducting interviews. We also collected corresponding environmental specimens in some households and their surroundings, selected by proximity to the index household.

[snip]

From each household's flock, we collected sick poultry and carcasses for subtype H5N1 virus testing, sampled 10 randomly selected ducks, and bled and swabbed cloacae and tracheas. (Vong et al., Emerging Infectious Diseases)

Good idea. Unfortunately the results are very badly presented and therefore difficult to interpret (doesn't EID have editors?). 167 samples were taken from 43 households. A careful back and forth reading suggests that 14 of the 43 households had environmental samples showing evidence of viral RNA (by rtPCR). 35% of the samples from these "viral" households were positive. Viral RNA were found in poultry feces, soil swab specimens, feathers from recently dead poultry and water plants in household ponds and mud. The paper also says viral RNA was found in "most and dry surfaces." Mud had the highest viral loads of the environmental samples. Interestingly, 4 of the 14 viral households had no history of poultry infection, although in three of the four birds had died. In one there were not even any bird deaths. They state that there was "no association" between flock deaths and positive environmental samples, although given the small sample sizes it isn't clear exactly what this means. However in households where there were reported poultry deaths, there was more likely to be a positive environmental sample if the last death was more recent. This might mean the viral RNA is only detectable over a defined period. Viral RNA was detectable up to 12 days from the last flock death in positive samples. So the virus is likely detectable at least that long.

What do we learn from this? Not as much as we might wish. Viral RNA seems fairly prevalent in the environment in the vicinity of backyard poultry outbreaks, but we don't know yet what this means since we don't know how often finding evidence of viral RNA means there is infection-capable virus around. While no virus could be isolated from the environmental samples, it does mean there was once virus there,. The authors note that small ponds are common near Cambodian households and they contain abundant quantities of duck feces. Children play and bathe in the ponds.

While the virus is currently not easily transmitted from birds to humans, or at least it seems to cause clinical illness infrequently despite high exposure, this kind of environmental exposure scenario plausibly represents a mechanism for the virus to find new non-bird hosts where it can continue to change and evolve. Nothing we have found out about this virus makes us rest any easier regarding its potential to become a major public health threat.

More like this

And in areas where AI is officially said to be endemic, food safety precautions are sorely lacking, even at high-end tourist sites.

See this short slide show posted on YouTube by "BahasaLady," entitled "Breakfast in Bird Flu Land."

http://tinyurl.com/6qh8xy

It shows runny eggs proudly served at a Bali (Indonesia) hotel in July 2008.

By Path Forward (not verified) on 31 Jul 2008 #permalink

It was my impression that it's the white part of the eggs that need to be cooked thoroughly. Must have missed something along the way. Personally I like my eggs over hard or scrambled but the husband does like the yellow part to be runny in degree.

"most and dry surfaces."

moist and dry surfaces. Got it.
What turned my stomach was the children who play in the same pond where the ducks crap. If anyone has been to a duck pond they realize the horrid mess these birds make.

find new non-bird hosts where it can continue to change and evolve

Key words there revere.
This bug wants to live just like everything else. Mankind is powerless in controlling it. Yes, great gains have been made however . . .

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/a….

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

it needn't be H5N1 and Cambodia.
Repeat similar examinations with other flu in other countries. That should already give useful hints.
Has it been done for human flu ?

Just wondering if it's possible for H5N1 to survive being taken up into the interior of plants from water, just as the salmonella was taken up into the stems of Spinach Plants from irrigation water?
If such plants were brought into a kitchen and served raw, as in a salad, would H5N1 likely be spread?

Poppy; There is uncertainty about whether H5N1 is transmissible through the gastrointestinal route and even if it is (I consider it possible but it depends on things we don't know yet) the scenario you describe you not likely deliver a sufficient infective dose. That's a guess but an educated guess.

I just saw a chilling thing on Globetrekkers, a show that seems to feature athletic and sprightly young people touring various parts of the world. A young woman was taking her viewers on an intriguing tour of China, quite fascinating actually. But it included a trip to a restaurant in which the woman sat down to a meal of apparently outrageously delicious duck.

Only thing was, when she showed how it was prepared the chef started by taking the raw, freshly killed duck up to his mouth and the he peoceeded to blow on one end, I guess to loosen the skin. Human lips blowing on raw duck skin. Isn't that a quick-quack way to disease...maybe even spread of H5N1?

By polyphony (not verified) on 02 Aug 2008 #permalink