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Global spread of H5N1

2007 Schools Wikipedia Selection. Related subjects: Environment

                  Highly pathogenic H5N1
   Highly pathogenic H5N1
    Countries with poultry or wild birds killed by H5N1.
    Countries with human cases of H5N1.

   The global spread of (highly pathogenic) H5N1 in birds is considered a
   significant pandemic threat.

   While prior H5N1 strains have been known, they were significantly
   different from the current H5N1 strain on a genetic level, making the
   global spread of this new strain unprecedented. The current H5N1 strain
   is a fast-mutating, highly pathogenic avian influenza virus (HPAI)
   found in multiple bird species. It is both epizootic (an epidemic in
   non-humans) and panzootic (a disease affecting animals of many species
   especially over a wide area). Unless otherwise indicated, "H5N1" in
   this article refers to the recent highly pathogenic strain of H5N1.

   "Since 1997, studies of H5N1 indicate that these viruses continue to
   evolve, with changes in antigenicity and internal gene constellations;
   an expanded host range in avian species and the ability to infect
   felids; enhanced pathogenicity in experimentally infected mice and
   ferrets, in which they cause systemic infections; and increased
   environmental stability."

   CAPTION: Cumulate Human Cases of and Deaths from H5N1
   As of April 11, 2007

   Image:H5n1 spread (with regression).png

   Notes:
     * Source WHO Confirmed Human Cases of H5N1
     * "[T]he incidence of human cases peaked, in each of the three years
       in which cases have occurred, during the period roughly
       corresponding to winter and spring in the northern hemisphere. If
       this pattern continues, an upsurge in cases could be anticipated
       starting in late 2006 or early 2007." Avian influenza –
       epidemiology of human H5N1 cases reported to WHO
     * The regression curve for deaths is y = a + e^k x, and is shown
       extended through the end of April, 2007.

   Tens of millions of birds have died of H5N1 influenza and hundreds of
   millions of birds have been slaughtered and disposed of to limit the
   spread of H5N1. Countries that have reported one or more major highly
   pathogenic H5N1 outbreaks in birds (causing at least thousands but in
   some cases millions of dead birds) are (in order of first outbreak
   occurrence): Korea, Vietnam, Japan, Thailand, Cambodia, Laos,
   Indonesia, China, Malaysia, Russia, Kazakhstan, Mongolia, Turkey,
   Romania, Croatia, Ukraine, Cyprus, Iraq, Nigeria, Egypt, India, France,
   Niger, Bosnia, Azerbaijan, Albania, Cameroon, Myanmar, Afghanistan,
   Israel, Pakistan, Jordan, Burkina Faso, Germany, Sudan, Ivory Coast,
   Djibouti, Hungary, United Kingdom, Kuwait, Bangladesh, Saudi Arabia,
   Ghana.

   Highly pathogenic H5N1 has been found in birds in the wild in numerous
   other countries: Austria, Bulgaria, Czech Republic, Denmark, Greece,
   Iran, Italy, Poland, Serbia and Montenegro, Slovakia, Slovenia, Spain,
   Sweden, Switzerland. Surveillance of H5N1 in humans, poultry, wild
   birds, cats and other animals remains very weak in many parts of Asia
   and Africa. Much remains unknown about the exact extent of its spread.

   H5N1 has low pathogenic varieties endemic in birds in North America.
   H5N1 has a highly pathogenic variety that is endemic in dozens of
   species of birds throughout south Asia and is threatening to become
   endemic in birds in west Asia and Africa. So far, it is very difficult
   for humans to become infected with H5N1. The presence of highly
   pathogenic (deadly) H5N1 around the world in both birds in the wild
   (swans, magpies, ducks, geese, pigeons, eagles, etc.) and in chickens
   and turkeys on farms has been demonstrated in millions of cases with
   the virus isolate actually sequenced in hundreds of cases yielding
   definitive proof of the evolution of this strain of this subtype of the
   species Influenzavirus A (bird flu virus).

   CAPTION: H5N1

     * Influenza A virus subtype H5N1
     * Genetic structure
     * Infection
     * Human mortality
     * Global spread

          + in 2006

     * Social impact
     * Pandemic

   WHO pandemic phases
    1. Low risk
    2. New virus
    3. Self limiting
    4. Person to person
    5. Epidemic exists
    6. Pandemic exists

   According to Robert Webster:

          "The epicenters of both the Asian influenza pandemic of 1957 and
          the Hong Kong influenza pandemic of 1968 were in Southeast Asia,
          and it is in this region that multiple clades of H5N1 influenza
          virus have already emerged. The Asian H5N1 virus was first
          detected in Guangdong Province, China, in 1996, when it killed
          some geese, but it received little attention until it spread
          through live-poultry markets in Hong Kong to humans in May 1997,
          killing 6 of 18 infected persons. [...] From 1997 to May 2005,
          H5N1 viruses were largely confined to Southeast Asia, but after
          they had infected wild birds in Qinghai Lake, China, they
          rapidly spread westward. [...] The intermittent spread to humans
          will continue, and the virus will continue to evolve." Map

Human and bird cases

   CAPTION: Confirmed human cases and mortality rate of avian influenza
   (H5N1)
   As of  April 11, 2007

   Country Report dates
   Total
   2003 2004 2005 2006 2007
   cases deaths cases deaths cases deaths cases deaths cases deaths cases
   deaths
   Flag of Azerbaijan  Azerbaijan   8 5 63%   8 5 63%
   Flag of Cambodia  Cambodia   4 4 100% 2 2 100% 1 1 100% 7 7 100%
   Flag of People's Republic of China  PR China 1 1 100%   8 5 63% 13 8
   62% 1 0 0% 23 14 61%
   Flag of Djibouti  Djibouti   1 0 0%   1 0 0%
   Flag of Egypt  Egypt   18 10 56% 16 4 25% 34 14 41%
   Flag of Indonesia  Indonesia   19 12 63% 56 46 82% 6 5 83% 81 63 78%
   Flag of Iraq  Iraq   3 2 67%   3 2 67%
   Flag of Laos  Laos   2 2 100% 2 2 100%
   Flag of Nigeria  Nigeria   1 1 100% 1 1 100%
   Flag of Thailand  Thailand   17 12 71% 5 2 40% 3 3 100%   25 17 68%
   Flag of Turkey  Turkey   12 4 33%   12 4 33%
   Flag of Vietnam  Vietnam 3 3 100% 29 20 69% 61 19 31%   93 42 45%
   Total 4 4 100% 46 32 70% 97 42 43% 116 80 69% 28 14 50% 291 172 59%
   Source: World Health Organization Communicable Disease Surveillance &
   Response (CSR)

1959-1997

   Ducks play a key role in H5N1 spread
   Ducks play a key role in H5N1 spread
     * A highly pathogenic strain of H5N1 caused flu outbreaks with
       significant spread to numerous farms, resulting in great economic
       losses in 1959 in Scotland in chickens and in 1991 in England in
       turkeys. These strains were somewhat similar to the current
       pathogenic strain of H5N1 in two of its ten genes, the gene that
       causes it to be type H5 and the gene that causes it to be N1. The
       other genes can and have been reassorted from other subtypes of the
       bird flu species (their ease at exchanging genes is part of what
       makes them all one species). Evolution by reassortment of H5N1 from
       1999 to 2002 created the Z genotype which became the dominant
       strain of highly pathogenic H5N1 in 2004 and is now spreading
       across the entire world in both wild and domestic birds.

     * "The precursor of the H5N1 influenza virus that spread to humans in
       1997 was first detected in Guangdong, China, in 1996, when it
       caused a moderate number of deaths in geese and attracted very
       little attention."

     * In 1997, in Hong Kong, 18 humans were infected and 6 died in the
       first known case of H5N1 infecting humans.

2003

     * "Human disease associated with influenza A subtype H5N1 re-emerged
       in January 2003, for the first time since an outbreak in Hong Kong
       in 1997." Three people in one family were infected after visiting
       Fujian province in mainland China and 2 died.

     * By midyear of 2003 outbreaks of poultry disease caused by H5N1
       occurred in Asia, but were not recognized as such. That December
       animals in a Thai zoo died after eating infected chicken carcasses.
       Later that month H5N1 infection was detected in 3 flocks in the
       Republic of Korea.

     * H5N1 in China in this and later periods is less than fully
       reported. Blogs have described many discrepancies between official
       China government announcements concerning H5N1 and what people in
       China see with their own eyes. Many reports of total H5N1 cases
       exclude China due to widespread disbelief in China's official
       numbers.

2004

   In January 2004 a major new outbreak of H5N1 surfaced in Vietnam and
   Thailand's poultry industry, and within weeks spread to ten countries
   and regions in Asia, including Indonesia, South Korea, Japan and China.
   In October 2004 researchers discovered H5N1 is far more dangerous than
   previously believed because waterfowl, especially ducks, were directly
   spreading the highly pathogenic strain of H5N1 to chickens, crows,
   pigeons, and other birds and that it was increasing its ability to
   infect mammals as well. From this point on, avian flu experts
   increasingly refer to containment as a strategy that can delay but not
   prevent a future avian flu pandemic.

2005

   The spread of avian influenza in the eastern hemisphere.
   The spread of avian influenza in the eastern hemisphere.

   In January 2005 an outbreak of avian influenza affected thirty three
   out of sixty four cities and provinces in Vietnam, leading to the
   forced killing of nearly 1.2 million poultry. Up to 140 million birds
   are believed to have died or been killed because of the outbreak. In
   April 2005 there begins an unprecedented die-off of over 6,000
   migratory birds at Qinghai Lake in central China over three months.
   This strain of H5N1 is the same strain as is spread west by migratory
   birds over at least the next ten months. In August 2005 H5N1 spread to
   Kazakhstan, Mongolia and Russia. On September 29, 2005, David Nabarro,
   the newly appointed Senior United Nations System Coordinator for Avian
   and Human Influenza, warned the world that an outbreak of avian
   influenza could kill 5 to 150 million people. David Nabarro later
   stated that as the virus had spread to migratory birds, an outbreak
   could start in Africa or the Middle East. Later in 2005 H5N1 spread to
   Turkey, Romania, Croatia and Kuwait.

2006

     * In the first two months of 2006 H5N1 spread to other Asian
       countries (such as India), north Africa, and Europe in wild bird
       populations possibly signaling the beginning of H5N1 being endemic
       in wild migratory bird populations on multiple continents for
       decades, permanently changing the way poultry are farmed. In
       addition, the spread of highly pathogenic H5N1 to wild birds, birds
       in zoos and even sometimes to mammals (example: pet cats) raises
       many unanswered questions concerning best practices for threat
       mitigation, trying to balance reducing risks of human and nonhuman
       deaths from the current nonpandemic strain with reducing possible
       pandemic deaths by limiting its chances of mutating into a pandemic
       strain. Not using vaccines can result in the need to kill
       significant numbers of farm and zoo birds, while using vaccines can
       increase the chance of a flu pandemic.

     * By April 2006 scientists had concluded that containment had failed
       due to the role of wild birds in transmitting the virus and were
       now emphasizing far more comprehensive risk mitigation and
       management measures.

     * In June 2006 WHO predicted an upsurge in human deaths due to H5N1
       during late 2006 or early 2007. In July and August 2006
       significantly increased numbers of bird deaths due to H5N1 were
       recorded in Cambodia, China, Laos, Nigeria, and Thailand while
       continuing unabated a rate unparalleled in Indonesia.

     * In September, Egypt and Sudan joined the list of nations seeing a
       resurgence of bird deaths due to H5N1.

     * In November and December, South Korea and Vietnam joined the list
       of nations seeing a resurgence of bird deaths due to H5N1.

2007

   In January, Japan, Hungary, Russia, and the United Kingdom joined the
   list of nations seeing a resurgence of bird deaths due to H5N1.

   In February, Pakistan, Turkey, Afghanistan, and Myanmar joined the list
   of nations seeing a resurgence of bird deaths due to H5N1; and Kuwait
   saw its first major outbreak of H5N1 avian flu.

   In March Bangladesh and Saudi Arabia each saw their first major
   outbreak of H5N1 avian flu; and Ghana in May.

January

     * January 14, 2007: "Japanese agricultural officials confirmed
       yesterday that the virulent H5N1 bird flu virus caused the deaths
       of thousands of chickens at a poultry farm in southern Japan this
       week [...] Japan's most recent [prior] outbreak occurred in Kyoto
       in 2004.".

     * January 17, 2007: Indonesia Works to Stem Bird Flu Cases -
       Indonesia plans to slaughter hundreds of thousands of backyard
       chickens over the next few weeks in a bid to stem a surge in human
       deaths from the H5N1 virus. Indonesia has recorded 61 deaths from
       bird flu, including four in the last week.

     * January 25, 2007:"The European Commission has confirmed the
       presence of [H5N1] in a farm in the southeastern Hungary."

     * January 29, 2007:There was an outbreak of H5N1 at three farms or
       households in the Krasnodar territory, an agricultural region in
       the southern part of European Russia on the Black Sea, Russian
       officials said on January 29, 2007.

February

     * February 3, 2007: In late January 2007 there was an outbreak of
       avian flu, caused by H5N1, at one of Bernard Matthews' farms in
       Holton in Suffolk. This infection, the second in the United
       Kingdom, was confirmed on 3 February 2007. A 3km protection zone,
       10km surveillance zone and a restricted zone encompassing 2000Km²
       were set up and 159,000 turkeys were slaughtered with the cull
       being completed on 5 February. Around 320 workers at the plant were
       given anti-viral drugs.The plant was thoroughly disinfected with
       cleaning complete on February 12 and permission being given for
       production to resume. Neither causation, nor a link with the
       Bernard Matthews plant in Hungary, has been established but the
       H5N1 bird flu strains found in geese in Hungary and the turkeys in
       Britain are 99.96% genetically identical, and almost certainly
       linked, according to an analysis of the viruses by the Veterinary
       Laboratories Agency in Weybridge, Surrey.

     * February 6, 2007: H5N1 was found in a flock of 40 chickens near
       Islamabad, Pakistan and all the chickens are now dead from the
       disease bird flu or culling to prevent its spread.

     * February 9, 2007: H5N1 killed 170 chickens in Bogazkoy village, in
       southeastern Turkey. Nearly 1,000 birds have been culled in
       Bogazkoy and two nearby villages."

     * February 22, 2007:"Afghan authorities were culling poultry after an
       outbreak of the deadly H5N1 strain of bird flu in chicken in an
       eastern Afghan city, a U.N. official said Wednesday."

     * February 25, 2007:Kuwait saw its first major outbreak of H5N1 avian
       flu.

     * February 28, 2007:"Myanmar reported that the H5N1 virus killed
       poultry at a farm about 5 miles from Rangoon, the country's largest
       city [...] The outbreak began 2 days ago, killing 68 of 1,360 layer
       chickens, ducks, and pullets, and officials attributed the outbreak
       to poor biosecurity on the farm, the report said. The remaining
       birds were destroyed, and authorities instituted several control
       measures including limiting poultry movement within the country,
       screening poultry, and disinfecting the affected area. Myanmar's
       last poultry outbreak was reported in April 2006."

March

     * March 22, 2007: Bangladesh saw its first major outbreak of H5N1
       avian flu. "The virus was found in the birds from a poultry firm
       run by Bangladesh's National Airlines Biman, which has already
       culled 30,000 birds over the last few days."

     * March 23, 2007: "Saudi Arabia's agriculture ministry has said the
       deadly H5N1 strain of bird flu had been discovered in [...]
       peacocks, turkeys, ostriches and parrots [and all] birds in the
       area had been culled. [...] The last reported cases of bird flu in
       Saudi Arabia involved 37 falcons in 2006. Last month, Saudi Arabia
       lifted bans going back to 2004 on poultry imports from 42
       countries."

May

     * May 03, 2007:"Ghana's first case of the highly pathogenic H5N1 bird
       flu has been confirmed in sick chickens by local laboratories and a
       US naval laboratory in Egypt, a World Health Organisation official
       said overnight. Some 1600 birds had already been incinerated as
       part of efforts to control the outbreak on a farm 20km east of
       Ghana's capital Accra, near the port of Tema".

Pig cases

   Pigs can harbor influenza viruses adapted to humans and others that are
   adapted to birds, allowing the viruses to exchange genes and create a
   pandemic strain.
   Pigs can harbour influenza viruses adapted to humans and others that
   are adapted to birds, allowing the viruses to exchange genes and create
   a pandemic strain.

   Avian influenza virus H3N2 is endemic in pigs (" swine flu") in China
   and has been detected in pigs in Vietnam, increasing fears of the
   emergence of new variant strains. Health experts say pigs can carry
   human influenza viruses, which can combine (i.e. exchange homologous
   genome sub-units by genetic reassortment) with H5N1, passing genes and
   mutating into a form which can pass easily among humans. H3N2 evolved
   from H2N2 by antigenic shift and caused the Hong Kong Flu pandemic of
   1968 and 1969 that killed up to 750,000 humans. The dominant strain of
   annual flu in humans in January 2006 is H3N2. Measured resistance to
   the standard antiviral drugs amantadine and rimantadine in H3N2 in
   humans has increased to 91% in 2005. A combination of these two
   subtypes of the species known as the avian flu virus in a country like
   China is a worst case scenario. In August 2004, researchers in China
   found H5N1 in pigs.

   In 2005 it was discovered that H5N1 "could be infecting up to half of
   the pig population in some areas of Indonesia, but without causing
   symptoms [...] Chairul Nidom, a virologist at Airlangga University's
   tropical disease centre in Surabaya, Java, [Indonesia] was conducting
   independent research earlier this year. He tested the blood of 10
   apparently healthy pigs housed near poultry farms in western Java where
   avian flu had broken out, Nature reported. Five of the pig samples
   contained the H5N1 virus. The Indonesian government has since found
   similar results in the same region, Nature reported. Additional tests
   of 150 pigs outside the area were negative."

Felidae (cats)

   Domestic cats can get H5N1 from eating birds, and can transmit it to
   other cats and possibly to people.
   Domestic cats can get H5N1 from eating birds, and can transmit it to
   other cats and possibly to people.

   "In Bangkok, Thailand, all the cats in one household are known to have
   died of H5N1 in 2004. Tigers and leopards in Thai zoos also died, while
   last year two cats near an outbreak in poultry and people in Iraq were
   confirmed to have died of H5N1, as were three German cats that ate wild
   birds. In Austria cats were infected but remained healthy". Cats in
   Indonesia were also found to have been infected with H5N1.

   The spread to more and more types and populations of birds and the
   ability of felidae (cats) to catch H5N1 from eating this natural prey
   means the creation of a reservoir for H5N1 in cats where the virus can
   adapt to mammals is one of the many possible pathways to a pandemic.

October 2004

   Variants have been found in a number of domestic cats, leopards and
   tigers in Thailand, with high lethality. "The Thailand Zoo tiger
   outbreak killed more than 140 tigers, causing health officials to make
   the decision to cull all the sick tigers in an effort to stop the zoo
   from becoming a reservoir for H5N1 influenza (ProMED-mail, 2004i;
   ProMED-mail, 2004w). A study of domestic cats showed H5N1 virus
   infection by ingestion of infected poultry and also by contact with
   other infected cats (Kuiken et al., 2004)." The initial OIE report
   reads: "the clinical manifestations began on 11 October 2004 with
   weakness, lethargy, respiratory distress and high fever (about 41-42
   degrees Celsius). There was no response to any antibiotic treatment.
   Death occurred within three days following the onset of clinical signs
   with severe pulmonary lesions."

February 28, 2006

   A dead cat infected with the H5N1 bird flu virus was found in Germany.

March 6, 2006

   Hans Seitinger, the top agriculture official in the southern state of
   Styria, Austria announced that several still living cats in Styria have
   tested positive for H5N1:

August 2006

   It was announced in the August 2006 CDC EID journal that while
   literature describing HPAI H5N1 infection in cats had been limited to a
   subset of clade I viruses; a Qinghai-like virus (they are genetically
   distinct from other clade II viruses) killed up to five cats and 51
   chickens from February 3 to February 5, 2006 in Grd Jotyar (~10 km
   north of Erbil City, Iraq). Two of the cats were available for
   examination.

          "An influenza A H5 virus was present in multiple organs in all
          species from the outbreak site in Grd Jotyar (Table). cDNA for
          sequencing was amplified directly from RNA extracts from
          pathologic materials without virus isolation. On the basis of
          sequence analysis of the full HA1 gene and 219 amino acids of
          the HA2 gene, the viruses from the goose and 1 cat from Grd
          Jotyar and from the person who died from Sarcapcarn (sequence
          derived from PCR amplification from first-passage egg material)
          are >99% identical at the nucleotide and amino acid levels
          (GenBank nos. DQ435200–02). Thus, no indication of virus
          adaptation to cats was found. The viruses from Iraq are most
          closely related to currently circulating Qinghai-like viruses,
          but when compared with A/bar-headed goose/Qinghai/65/2005 (H5N1)
          (GenBank no. DQ095622), they share only 97.4% identity at the
          nucleic acid level with 3 amino acid substitutions of unknown
          significance. On the other hand, the virus from the cat is only
          93.4% identical to A/tiger/Thailand/CU-T4/2004(H5N1) (GenBank
          no. AY972539). These results are not surprising, given that
          these strains are representative of different clades (8,9).
          Sequencing of 1,349 bp of the N gene from cat 1 and the goose
          (to be submitted to GenBank) show identity at the amino acid
          level, and that the N genes of viruses infecting the cat and
          goose are >99% identical to that of A/bar-headed
          goose/Qinghai/65/2005(H5N1). These findings support the notion
          that cats may be broadly susceptible to circulating H5N1 viruses
          and thus may play a role in reassortment, antigenic drift, and
          transmission."

January 24, 2007

   "Chairul Anwar Nidom of Airlangga University in Surabaya, Indonesia,
   told journalists last week that he had taken blood samples from 500
   stray cats near poultry markets in four areas of Java, including the
   capital, Jakarta, and one area in Sumatra, all of which have recently
   had outbreaks of H5N1 in poultry and people. Of these cats, 20 per cent
   carried antibodies to H5N1. This does not mean that they were still
   carrying the virus, only that they had been infected - probably through
   eating birds that had H5N1. Many other cats that were infected are
   likely to have died from the resulting illness, so many more than 20
   per cent of the original cat populations may have acquired H5N1."

Mammals in general

   Martens and an unknown number of other mammals can catch H5N1,
   illustrating the unprecedented ability of H5N1 to survive and spread.
   Martens and an unknown number of other mammals can catch H5N1,
   illustrating the unprecedented ability of H5N1 to survive and spread.

   H5N1 has been transmitted in laboratories to many species including
   mice and ferrets to study its effects.

   H5N1 was transmitted in the wild to three civet cats in Vietnam in
   August 2005 and a stone marten in Germany in March 2006.

   The BBC reported that a stray dog in Azerbaijan died from the disease
   on March 15, 2006.

   Experts believe more work is needed to determine the role of mammals in
   the epidemiology of H5N1. Officials are not doing enough to monitor
   cats, dogs and other carnivores for their possible role in transmitting
   H5N1. People living in areas where the A(H5N1) virus has infected birds
   are advised to keep their cats indoors. "Cats can be infected through
   the respiratory tract. Cats can also be infected when they ingest the
   virus, which is a novel route for influenza transmission in mammals.
   But cats excrete only one-thousandth the amount of virus that chickens
   do [...] The concern is that if large numbers of felines and other
   carnivores become infected, the virus might mutate in a series of
   events that could lead to an epidemic among humans. Dogs, foxes, seals
   and other carnivores may be vulnerable to A(H5N1) virus infection, Dr.
   Osterhaus said. Tests in Thailand have shown that the virus has
   infected dogs without causing apparent symptoms."

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