Influenza pandemic

Pandemic flu viruses have some avian flu virus genes and usually some human flu virus genes. Both the H2N2 and H3N2 pandemic strains contained genes from avian influenza viruses. The new subtypes arose in pigs coinfected with avian and human viruses and were soon transferred to humans. Swine were considered the original "intermediate host" for influenza, because they supported reassortment of divergent subtypes. However, other hosts appear capable of similar coinfection (e.g., many poultry species), and direct transmission of avian viruses to humans is possible.The Spanish flu virus strain may have been transmitted directly from birds to humans.

In spite of their pandemic connection, avian influenza viruses are noninfectious for most species. When they are infectious they are usually asymptomatic, so the carrier does not have any disease from it. Thus while infected with an avian flu virus, the animal doesn't have a "flu". Typically, when illness (called "flu") from an avian flu virus does occur, it is the result of an avian flu virus strain adapted to one species spreading to another species (usually from one bird species to another bird species). So far as is known, the most common result of this is an illness so minor as to be not worth noticing (and thus little studied). But with the domestication of chickens and turkeys, humans have created species subtypes (domesticated poultry) that can catch an avian flu virus adapted to waterfowl and have it rapidly mutate into a form that kills in days over 90% of an entire flock and spread to other flocks and kill 90% of them and can only be stopped by killing every domestic bird in the area. Until H5N1 infected humans in the 1990s, this was the only reason avian flu was considered important. Since then, avian flu viruses have been intensively studied; resulting in changes in what is believed about flu pandemics, changes in poultry farming, changes in flu vaccination research, and changes in flu pandemic planning.

H5N1 has evolved into a flu virus strain that infects more species than any previously known flu virus strain, is deadlier than any previously known flu virus strain, and continues to evolve becoming both more widespread and more deadly causing Robert Webster, a leading expert on avian flu, to publish an article titled "The world is teetering on the edge of a pandemic that could kill a large fraction of the human population" in American Scientist. He called for adequate resources to fight what he sees as a major world threat to possibly billions of lives.Since the article was written, the world community has spent billions of dollars fighting this threat with limited success.

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Bird Flu Vaccines: What is Taking So Long?

With the current development of a vaccine for the H5N1 strain of the Bird Flu Virus still 2 to 3 years away. We don’t have much of a choice but to really be very cautious that the H5N1 strain does not mutate with a human flu virus.

If the outbreak we fear does happen without the vaccines ready yet, all we can

possibly do is just quarantine the geographical area where the virus is rampant. Give them the vaccines that have been developed and prevent them from spreading it further. This will only work if the outbreak is limited geographically. When the outbreak does happen to 10,000 places, we’re in Big S*%T.

The development of a vaccine is so slow because we still use methods dating back 50 years ago. Ironically this is because they still use chicken eggs to develop the vaccines. New methods are on the horizon, instead of using chicken eggs, they may be able to use mammal cells.

Scientist would be storing the mammal cells in large numbers. So that when a flu strain or threat develops, they can just inject it to the cells. The injected cells will then burst and die. The scientist will then harvest the proteins of the influenza and distribute them as vaccines already.

Vaccines made from DNA are really appealing because they could be made and administered quickly. However this kind of vaccine is still being tested on humans. DNA vaccine works by attaching itself to a segment of our DNA. It contains the coded information of the flu virus’ protein.
by: Michael Colucci
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Avian Influenza: Current H5N1 Situation

The highly pathogenic avian influenza A (H5N1) epizootic (animal outbreak) in Asia, Europe, the Near East, and Africa is not expected to diminish significantly in the short term. It is likely that H5N1 virus infections among domestic poultry have become endemic in certain areas and that 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 has been very rare, limited and unsustained. However, this epizootic continues to pose an important public health threat.

There is little pre-existing natural immunity to H5N1 virus infection in the human population. If H5N1 viruses gain the ability for efficient and sustained transmission among humans, an influenza pandemic could result, with potentially high rates of illness and death worldwide. No evidence for genetic reassortment between human and avian influenza A virus genes has been found to date, and there is no evidence of any significant changes to circulating H5N1 virus strains to suggest greater transmissibility to or among humans. Genetic sequencing of avian influenza A (H5N1) viruses from human cases in Vietnam, Thailand, and Indonesia shows resistance to the antiviral medications amantadine and rimantadine, two of the medications commonly used for treatment of influenza. This leaves two remaining antiviral medications (oseltamivir and zanamivir) that should still be effective against currently circulating strains of H5N1 viruses. A small number of oseltamivir resistant H5N1 virus infections of humans have been reported. Efforts to produce pre-pandemic vaccine candidates for humans that would be effective against avian influenza A (H5N1) viruses are ongoing. However, no H5N1 vaccines are currently available for human use.

Research suggests that currently circulating strains of H5N1 viruses are becoming more capable of causing disease (pathogenic) in animals than were earlier H5N1 viruses. One study found that ducks infected with H5N1 virus are now shedding more virus for longer periods without showing symptoms of illness. This finding has implications for the role of ducks in transmitting disease to other birds and possibly to humans as well. Additionally, other findings have documented H5N1 virus infection among pigs in China and Vietnam; H5N1 virus infection of cats (experimental infection of housecats in the Netherlands, isolation of H5N1 virus from domestic cats in Germany and Thailand, and detection of H5N1 viral RNA in domestic cats in Iraq and Austria); H5N1 virus infection of dogs (isolation of H5N1 virus from a domestic dog in Thailand); and isolation of H5N1 viruses from tigers and leopards at zoos in Thailand). In addition, H5N1 virus infection in a wild stone marten (a weasel-like mammal) was reported in Germany and in a wild civet cat in Vietnam. Avian influenza A (H5N1) virus strains that emerged in Asia in 2003 continue to evolve and may adapt so that other mammals may be susceptible to infection as well.
Notable findings of epidemiologic investigations of human H5N1 cases include:

* Thailand, 2004: An investigation concluded that probable limited human-to-human spread of influenza A (H5N1) had occurred in a family as a result of prolonged and very close contact between an ill child and her mother in a hospital. Transmission did not continue beyond one person.
* Vietnam, 2004: While the majority of known human H5N1 cases have begun with respiratory symptoms, one atypical fatal H5N1 case in a child in southern Vietnam presented with fever, diarrhea and seizures, and was initially diagnosed as encephalitis. The etiology was identified retrospectively as H5N1 virus through testing of cerebrospinal fluid, fecal matter, and throat and serum samples. Further research is needed to ascertain the implications of such findings.
* Vietnam, 2005: Investigations suggest transmission of H5N1 viruses to two persons through consumption of uncooked duck blood.
* Azerbaijan, 2006: Investigations revealed contact with H5N1-infected wild dead birds (swans) as the most plausible source of infection in several cases in teenagers involved in removing feathers from the birds.
* Indonesia, 2006: WHO reported evidence of limited human-to-human spread of H5N1 virus. In this situation, 8 people in one family were affected, with 7 deaths. H5N1 virus was isolated from 7 cases. The first family member is thought to have become ill through contact with infected poultry. This person then infected six family members. One of those six people (a child) then infected another family member (his father). No further spread outside of the exposed family was documented or suspected.
* Vietnam, 2006: A study reported a correlation between high H5N1 viral concentration and elevated inflammatory cytokine levels in fatal cases. The authors concluded that early antiviral treatment is needed to suppress H5N1 viral replication to prevent the inflammatory response that appears to be implicated in the pathogenesis of H5N1 virus infection.

Human H5N1 Cases

(WHO) has reported human cases of avian influenza A (H5N1) in Asia, Africa, the Pacific, Europe and the Near East. Indonesia and Vietnam have reported the highest number of H5N1 cases to date. Overall mortality in reported H5N1 cases is approximately 60%. The majority of cases have occurred among children and adults aged less than 40 years old. Mortality was highest in cases aged 10-19 years old. Studies have documented the most significant risk factors for human H5N1 infection to be direct contact with sick or dead poultry or wild birds, or visiting a live poultry market. Most human H5N1 cases have been hospitalized late in their illness with severe respiratory disease. A small number of clinically mild H5N1 cases have been reported. The current cumulative number of confirmed human cases of avian influenza A/(H5N1) is available on the WHO Avian Influenza website. Despite the high mortality, human cases of H5N1 remain rare to date.
Clusters of Human H5N1 Cases

Clusters of human H5N1 cases ranging from 2-8 cases per cluster have been identified in most countries that have reported H5N1 cases. Nearly all of the cluster cases have occurred among blood-related family members living in the same household. Whether such clusters are related to genetic or other factors is currently unknown. While most people in these clusters have been infected with H5N1 virus through direct contact with sick or dead poultry or wild birds, limited human-to-human transmission of H5N1 virus cannot 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 Near East. View the update on avian influenza in animals from the World Organization for Animal Health Web site.
Bird Import Ban

There is currently a ban on the importation of birds and bird products from H5N1-affected countries. 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 specified countries. For more information, see Embargo of Birds from Specified Countries.
Travel

Updated Information for Travelers about Avian Influenza A(H5N1) is available at the CDC Travelers’ Health Web site. Also see Guidelines and Recommendations - Interim Guidance about Avian Influenza A (H5N1) for U.S. Citizens Living Abroad.
CDC Response

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) on development of a vaccine for influenza A (H5N1). For more information view CDC's Response to Avian Influenza.

* Also see Updated Interim Guidance for Laboratory Testing of Persons with Suspected Infection with Avian Influenza A (H5N1) Virus in the United States for CDC’s domestic H5N1 surveillance recommendations.

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

* Recommendations and laboratory procedures for detection of avian influenza A(H5N1) virus in specimens from suspected human cases (pdf 165K, 28 pages)
* WHO guidelines for investigation of human cases of avian influenza A(H5N1) (pdf 115K, 18 pages)
* Collecting, preserving and shipping specimens for the diagnosis of avian influenza A(H5N1) virus infection Guide for field operations (pdf 2.36M, 83 pages)

Background on the Current Outbreaks

Highly pathogenic avian influenza A (H5N1) virus is an influenza A virus subtype that occurs mainly in birds and is highly contagious among birds, causing high mortality among domestic poultry. Outbreaks of highly pathogenic H5N1 among poultry and wild birds are ongoing in a number of countries. Currently, there are two different groups (or clades) of H5N1 viruses circulating among poultry (clade 1, and clade 2 viruses). At least three subgroups or subclades of clade 2 H5N1 viruses have infected humans to date: subclades 2.1, 2.2, and 2.3 viruses. H5N1 virus infections of humans are rare and most cases have been associated with direct poultry contact during poultry outbreaks. While the H5N1 virus does not now infect people easily, infection in humans is very serious when it occurs; so far, more than half of people reported infected have died. Rare cases of limited human-to-human spread of H5N1 virus may have occurred, but there is no evidence of sustained human-to-human transmission.

Nonetheless, because all influenza viruses have the ability to change, scientists are concerned that H5N1 viruses one day could be able to infect humans more easily and spread easily from one person to another. Because H5N1 viruses have not infected many humans worldwide, 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 H5N1 virus transmission occurred. Experts from around the world are watching the H5N1 situation very closely and are preparing for the possibility that H5N1 viruses may begin to spread more easily from person to person.

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