Monday, 11 February 2008

Avian Influenza: Current H5N1 Situation

On this page:

* Assessment of the current situation
* The cases of human H5N1 infection
* Clusters of Human H5N1 Cases
* Animal H5N1 cases
* A ban on imports of birds
* Travel
* Response by CDC
* Background on the current outbreaks

Outbreaks of avian influenza
* Current Situation
* Past outbreaks
* Embargo of Birds
* Executive Order Quarantine
(From the White House)
* Quarantine Order Q & A

Assessment of the current situation

The highly pathogenic avian influenza A (H5N1) is an epizootic (animal epidemic) in Asia, Europe, the Middle East and Africa should not diminish significantly in the short term. It is likely that H5N1 infection among domestic poultry have become endemic in some areas and that the sporadic human infections resulting from direct contact with infected poultry and / or wild birds will continue to occur. So far, the spread of H5N1 virus from person to person is very rare, limited and sporadic. However, the epidemic continues to pose a significant threat to public health.

There is little pre-existing natural immunity to infection with the H5N1 virus in the human population. If the H5N1 virus acquire the transmission capacity efficient and sustained between humans, an influenza pandemic could result, with potentially high rates of illness and death in the world. No evidence for genetic reassortment between human and avian influenza A virus genes has been found so far, and there is no evidence of any significant change in the circulation of H5N1 virus strains suggest or greater transmissibility among humans. Genetic sequencing of avian influenza A (H5N1) virus human cases in Vietnam, Thailand and Indonesia shows resistance to antiviral drugs amantadine and rimantadine, two of the drugs commonly used to treat influenza. That leaves two other antiviral medications (oseltamivir and zanamivir), which must still be effective against currently circulating strains of H5N1 virus. A small number of oseltamivir-resistant infections of the H5N1 virus humans have been reported. Efforts to produce a vaccine against the pandemic pre-candidates for the man who would be effective against avian influenza A (H5N1) viruses are under way. However, no H5N1 vaccine is currently available for human use.

The research suggests that currently circulating strains of H5N1 viruses are becoming more capable of causing disease (pathogens) in animals than were previously H5N1 virus. One study found that ducks infected with the H5N1 virus are now shedding more virus for longer periods without showing symptoms of illness. This discovery has implications for the role of ducks in the transmission of the disease to other birds to humans, and perhaps also. In addition, other findings have documented infection with the H5N1 virus in pigs in China and Vietnam, the H5N1 infection in cats (experimental infection of the housecats in the Netherlands, the isolation of H5N1 virus of domestic cats in Germany and Thailand, and the detection of viral RNA in internal Cats H5N1 in Iraq and Austria), H5N1 infection in dogs (isolation of the H5N1 virus from a dog domestic Thailand), and isolation of H5N1 viruses from tigers and leopards in zoos in Thailand). In addition, infection with the H5N1 virus in a wild rock (a weasel-like mammal) has been reported in Germany and in a wild civet cat in Vietnam. Avian influenza A (H5N1) virus strains that have emerged in Asia in 2003, will continue to evolve and can be adapted so that other mammals may be susceptible to infection as well.
The findings of epidemiological investigations of human H5N1 cases are:

* Thailand, 2004: An investigation concluded that probable limited human-to-human spread of the influenza A (H5N1) occurred in a family in the wake of prolonged and very close contact between an ill child and her mother in a hospital . The transmission has not continued beyond one person.
* Vietnam, 2004: While the majority of known cases of human H5N1 infection have begun with respiratory symptoms, a deadly H5N1 atypical case in a child in southern Vietnam presented with fever, diarrhea and convulsions , and was initially diagnosed as encephalitis. The cause has been identified retrospectively from the H5N1 virus through testing of cerebrospinal fluid, feces, and throat and serum samples. Further research is needed to determine the implications of these findings.
* Vietnam, 2005: The surveys suggest transmission of H5N1 viruses to two persons through consumption of raw duck blood.
* Azerbaijan, 2006: The investigations revealed contacts with infected by the H5N1 dead wild birds (swans), the most plausible source of infection in many cases, eliminating adolescents involved in the feathers of a bird.
* Indonesia, 2006: WHO reported little evidence of human-to-human spread of H5N1 virus. In this situation, 8 people in one family have been affected, including 7 deaths. H5N1 virus was isolated from 7 cases. The first family member, it is believed, have become ill from contact with infected poultry. That person then infected six family members. One of those six people (one child), then another family member infected (his father). No other outside the family has been exposed documented or suspected.
* Vietnam, 2006: A study reported a correlation between high concentration H5N1 virus and high levels of inflammatory cytokines in fatal cases. The authors conclude that early treatment with antiviral agents is necessary to eliminate the H5N1 viral replication to prevent the inflammatory response that appears to be implicated in the pathogenesis of infection by the H5N1 virus.

Some cases of human H5N1 infection

(WHO) has reported human cases of avian influenza A (H5N1) in Asia, Africa, the Pacific, Europe and the Middle East. Indonesia and Vietnam have reported the highest number of H5N1 cases so far. Overall mortality in H5N1 cases reported is about 60%. The majority of cases occurred among children and adults aged under 40 years. Mortality was higher in cases aged 10-19 years. Studies have documented the most important risk factors for H5N1 infection in humans are in direct contact with dead or diseased poultry or wild birds, or visiting a live poultry market. Most cases of human H5N1 infection have been hospitalized late in the disease with severe respiratory disease. A small number of clinically mild H5N1 cases were reported. The current cumulative number of confirmed human cases of avian influenza A / (H5N1) is available on the WHO website on Avian Influenza. Despite the high mortality rate, human cases of H5N1 are still rare at this time.
Clusters of cases of human H5N1 infection

Clusters of cases of human H5N1 cases ranging from 2-8 in clusters have been identified in most countries that have reported cases of avian influenza H5N1. Almost all of the cluster of cases occurred between the blood-related members of the family living under one roof. If such groups are linked to other genetic factors or is currently unknown. While most people in these groups have been infected with the H5N1 virus through direct contact with sick or dead poultry or wild birds, limited human-to-human transmission of H5N1 can not be excluded in some clusters.
Animal H5N1 cases

Since December 2003, avian influenza A (H5N1) virus infections in animals have been reported in Asia, Africa, the Pacific, Europe and the Middle East. See the update on avian influenza in animals of the World Organization for Animal Health Web site.
Ban on the importation of birds

There is currently a ban on the importation of birds and bird products from countries affected by the H5N1 virus. The regulation states that no person may import or attempt to import any birds (Class Aves), whether dead or alive, or any products derived from birds (including hatching eggs), from the country. For more information, see the embargo Bird Specified Countries.

Updated travel information on avian influenza A (H5N1) is available at the CDC Travelers' Health website. See also Guidelines and Recommendations - Orientation on Avian Influenza A (H5N1) for American citizens living abroad.
Response by CDC

CDC is working with WHO and other international partners to monitor the situation closely. In addition, CDC continues to work with WHO and the National Institutes of Health (NIH), the development of a vaccine against influenza A (H5N1). For more information visit the CDC's response to bird flu.

* See also Updated Interim Guidance for laboratory tests involving people suspected of infection with avian influenza A (H5N1) virus in the United States for the CDC surveillance inside H5N1 recommendations.

The World Health Organization has additional resources and information on avian influenza A H5N1, which

* Recommendations and laboratory procedures for the detection of avian influenza A (H5N1) virus in samples of suspected human cases (165K pdf, 28 pages)
* WHO guidelines for investigating human cases of avian influenza A (H5N1) (115K pdf, 18 pages)
* The collection, preservation and transport of samples for the diagnosis of avian influenza A (H5N1) virus infection as a guide for field operations (2.36M pdf, 83 pages)

Background on the current outbreaks

Highly pathogenic avian influenza A (H5N1) virus is a subtype of influenza A virus that occurs mainly in birds and is highly contagious among birds, causing a high mortality rate among domestic poultry. Outbreaks of highly pathogenic H5N1 among poultry and wild birds are underway in a number of countries. Currently, there are two different groups (or clades) of H5N1 virus circulating among poultry (clade 1 and clade 2 virus). At least three sub-groups or sub-clade 2 of the H5N1 virus has infected humans date: sub-2, 1, 2.2, 2.3 and viruses. Virus H5N1 human infections are rare, and most cases have been linked to direct contact poultry during outbreaks in poultry. While H5N1 is not now easily infect people, human infection is very serious when it occurs, so far, more than half of those infected have died. Rare cases of limited human-to-human spread of H5N1 virus may have occurred, but there is no proof of human-to-human transmission.

However, because all influenza viruses have the ability to change, scientists are concerned that the H5N1 virus could one day be able to infect humans more easily and spread easily from one person to another. Because the H5N1 virus is not infected with a lot of men around the world, there is little or no immune protection against them in the human population and an influenza pandemic (worldwide outbreak of disease) could begin if sustained transmission of H5N1 have occurred. Experts from around the world are watching the H5N1 situation very closely and are preparing for the possibility that the H5N1 virus may begin to spread more easily from person to person.

1 komentar:

Dipl.-Ing. Wilfried Soddemann said...

Spread of avian flu by drinking water

Infected birds and poultry can everywhere contaminate the drinking water. All humans have very intensive contact to drinking water. To prove 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.
There is a widespread link between avian flu and water, e.g. in Egypt to the Nile delta or Indonesia to residential districts of less prosperous humans with backyard flocks and without central water supply as in Vietnam:
See also the WHO web side: and
“Influenza: Initial introduction of influenza viruses to the population via abiotic water supply versus biotic human viral respirated droplet shedding” and
“Transmission of influenza A in human beings”.
Avian flu infections may increase in consequence to increase of virus circulation. 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.
In hot climates/the tropics flood-related influenza is typical after extreme weather and floods. Virulence of influenza viruses depends on temperature and time. Special in cases of local water supplies with “young” and fresh H5N1 contaminated water from low local wells, cisterns, tanks, rain barrels, ponds, rivers or rice paddies this pathway can explain small clusters in households. At 24°C e.g. in the tropics the virulence of influenza viruses in water amount to 2 days. In temperate climates for “older” water from central water supplies cold water is decisive to virulence of viruses. At 7°C the virulence of influenza viruses in water amount to 14 days.
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.

Dipl.-Ing. Wilfried Soddemann - Free Science Journalist -

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