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franklanguage) wrote2007-09-01 10:06 am
Fwd: Study confirms human-human spread of bird flu
Study confirms human-human spread of bird flu
Updated Wed. Aug. 29 2007 10:43 AM ET
CTV.ca News Staff
A new analysis has confirmed that bird flu spread from person to person in Indonesia in April, U.S. researchers report in what appears to be a disturbing development for the infectious disease.
Health officials around the world have been closely monitoring the H5N1 strain of avian influenza spreading among birds from Asia to Africa to Europe.
So far, the strain rarely infects humans. But infectious disease experts are worried if it evolves so that it can spread easily from person to person, it may be the source of the next influenza pandemic, for which the globe is thought to be well overdue.
Since 2003, H5N1 has infected 322 people and killed 195. Most have been infected directly by birds. But a few clusters of cases have been noted for which no other explanation can be found except person-to-person transmission.
Biostatistician Ira Longini and colleagues at the Fred Hutchinson Cancer Research Center in Seattle looked at two such recent clusters -- one in which eight family members died in Sumatra in 2006, and another in Turkey, in which eight people were infected and four died.
Experts were almost certain the Sumatra cases were human-to-human transmission, but were eager to see more proof. Longini's team claims they have found that proof, reporting in the journal Emerging Infectious Diseases.
Using a computerized disease-transmission model that took into account the number of infected cases, the number of people potentially exposed, the viral-incubation period and other parameters, the researchers produced the first statistical confirmation of humans contracting the disease from each other.
How the cluster likely spread
The cluster likely began with a 37-year-old woman, who had been exposed to dead poultry and chicken feces, the presumed source of infection. She then probably passed the virus to her 10-year-old nephew who then passed it to his father.
The possibility that the boy infected his father was supported by genetic sequencing data. Other person-to-person transmissions in the cluster were backed up with statistical data.
All but one of the flu victims died.
Local health authorities eventually placed more than 50 relatives and close contacts under voluntary quarantine and the infections stopped. But Longini's team does not believe the quarantine did the trick; they believe the virus simply burned out.
"It went two generations and then just stopped, but it could have gotten out of control," Longini said in a statement.
"The world really may have dodged a bullet with that one, and the next time, we might not be so lucky."
The researchers now estimate the secondary-attack rate, which is the risk that one person will infect another, is at about 29 per cent. This is similar to what is seen for regular, seasonal influenza A in the United States.
As for the cluster in Turkey, Longini's team could not find statistical evidence of human-to-human transmission.
"There probably was person-to-person spread there as well but we couldn't get all the information we needed for the analysis," biostatistician Yang Yang said.
Longini's team also says they have developed a tool to run quick tests on disease outbreaks to see if dangerous epidemics or pandemics may be developing. The software product, called TranStat, would be available free of charge on the National Institutes of Health's Models of Infectious Disease Agent Study, or MIDAS, website.
H5N1 avian flu: Spread by drinking water
Initial introduction of influenza viruses to the population via abiotic water supply versus biotic human viral respirated droplet shedding
The primary, initial transmission of the human influenza epidemics by the biotic droplet infection is not proven and extremely improbably as influenza epidemics
• appear only in 9% of the cases (season 2004/2005 in Germany) together with recognized clusters.
• appear virologically locally singularly (influenza-subtypes and precision typing).
• appear geographically locally singularly.
• are not proven with priority in large cities and densely populated areas.
• appear predominantly in the colder regions of Germany.
• regularly reach their maxima in certain districts/cities.
• in temperate climates strictly run parallel to the course of the sum of coldness during the winter.
• can hardly spread via saliva droplets. Saliva contains far less Influenza viruses than the - heavier - droplets from throat and nose.
In temperate climates Influenza epidemics run strictly parallel to the course of the sum of coldness during winter. In hot climates/tropics the flood-related influenza is typical after extreme weather and natural after a flood. Virulence of influenza virus depends on temperature and time. If young and fresh contaminated water from a local low well, a cistern, tank, rain barrel or rice field is used water temperature may be higher. In Germany about 98% inhabitants have a central public water supply with older and better protected water. In Germany therefore coldness is decisive as to virulence of influenza viruses in drinking water.
Human influenza viruses could be proven in the excretions of mammals such as pigs (faecal and oronasal), wild boar (faecal and oronasal), cattle and goats, so that the transmission path from the environment over waters and the drinking water in principle is possible.
Drinking water is often not or only roughly filtered. Small viruses are not definitely removed thereby.
"Cooling chain of the public water supply"
Coldness is by far the most important parameter for the preservation of virulent influenza viruses in water. The soil temperatures in a meter of depth correspond to the temperatures of the drinking water pipelines that are laid frost-protected in the soils. The temperature minima of the soil temperatures in a 100 cm depth value in Germany during the months February and March 3-5°C and follows in particular the run of the wintry cold sum. Cold by influenza viruses contaminated drinking water can be the abiotic vehicle, which conserves virulent influenza viruses in the winter at 4-5°C and transports them over the "cooling chain of the public water supply" to humans during the months February and March.
Infections by drinking water will not be transmitted alone by drinking the water. Further transmission paths are the inhalation of aerosols and the contact with the drinking water. Access for humans are the conjunctiva, the nose mucous membrane, the mouth mucous membrane, the eardrum, wounds and by catheters affected other mucous membranes.
Conclusions
The primary transmission of the influenza by the biotic “warm” droplet infection from human to human is, already because of the strict dependence on environmental temperatures in temperate climates, extremely improbable. The influenza must be triggered by an abiotic vehicle, which is increasingly efficient regarding the spread of infections with increasingly cold environmental temperatures. Therefore it has to be searched for abiotic vehicles dependent on cold environmental temperatures for the transmission of the influenza in temperate climates. Drinking water is such an abiotic vehicle. The stated references and indications show that cold drinking water can be that abiotic vehicle, by which virulent human Influenza viruses from the reservoirs reach humans and triggers predominantly the seasonal influenza epidemics. That applies in particular also to the extremely lethal H5N1 bird flu, whose faecal transmission is indisputable.
Dipl.-Ing. Wilfried Soddemann
soddemann-aachen@t-online.de
no subject
The same!
I left chowhound years ago, and unfortunately Jim has never replied to my e-mails since. I've been vegetarian for over six years now, so maybe it's just as well; I hang out a lot at Isa Chandra Moskowitz' page now. (Just one word: cupcakes!)
So I added you as a friend, okay?
Beth (using Frank's account)
Re: The same!
So it's not just me...