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This page includes the World Health Organisiation's (WHO) 10 key Avian
Influenza facts as well as their more recent Avian Influenza Factsheet
produced in January 2006.
Ten things you need to know about
pandemic influenza
1. Pandemic influenza is different from avian flu
Avian flu refers to a large group of different influenza viruses
that primarily affect birds. On rare occasions, these bird viruses
can infect other species, including pigs and humans. The vast majority
of avian flu viruses do not infect humans. An influenza pandemic happens
when a new subtype emerges that has not previously circulated in humans.
For this reason, avian H5N1 is a strain with pandemic potential,
since it might ultimately adapt into a strain that is contagious among
humans. Once this adaptation occurs, it will no longer be an avian
flu virus -- it will be a human influenza virus. Influenza pandemics
are caused by new influenza viruses that have adapted to humans.
2. Influenza pandemics are recurring events
An influenza pandemic is a rare but recurrent event. Three pandemics
occurred in the previous century: “Spanish influenza”
in 1918, “Asian influenza” in 1957, and “Hong Kong
influenza” in 1968. The 1918 pandemic killed an estimated 40–50
million people worldwide. That pandemic, which was exceptional, is
considered one of the deadliest disease events in human history. Subsequent
pandemics were much milder, with an estimated 2 million deaths in
1957 and 1 million deaths in 1968.
A pandemic occurs when a new influenza virus emerges and starts spreading
as easily as normal influenza – by coughing and sneezing. Because
the virus is new, the human immune system will have no pre-existing
immunity. This makes it likely that people who contract avian influenza
will experience more serious disease than that caused by normal influenza.
3. The world may be on the brink of another pandemic
Health experts have been monitoring a new and extremely severe avian
influenza virus – the H5N1 strain – for almost eight years.
The H5N1 strain first infected humans in Hong Kong in 1997, causing
18 cases, including six deaths. Since mid-2003, this virus has caused
the largest and most severe outbreaks in poultry on record. In December
2003, infections in people exposed to sick birds were identified.
Since then, over 100 human cases have been laboratory confirmed in
four Asian countries (Cambodia, Indonesia, Thailand, and Viet Nam),
and more than half of these people have died. Most cases have occurred
in previously healthy children and young adults. Fortunately, the
virus does not jump easily from birds to humans or spread readily
and sustainably among humans. Should H5N1 evolve to a form as contagious
as normal influenza, a pandemic could begin.
4. All countries will be affected
Once a fully contagious virus emerges, its global spread is considered
inevitable. Countries might, through measures such as border closures
and travel restrictions, delay arrival of the virus, but cannot stop
it. The pandemics of the previous century encircled the globe in 6
to 9 months, even when most international travel was by ship. Given
the speed and volume of international air travel today, the virus
could spread more rapidly, possibly reaching all continents in less
than 3 months.
5. Widespread illness will occur
Because most people will have no immunity to the pandemic virus,
infection and illness rates are expected to be higher than during
seasonal epidemics of normal influenza. Current projections for the
next bird
flu pandemic estimate that a substantial percentage of
the world’s population will require some form of medical care.
Few countries have the staff, facilities, equipment, and hospital
beds needed to cope with large numbers of people who suddenly fall
ill.
6. Medical supplies such as bird flu vaccine and antiviral drugs
will be inadequate
Supplies of bird
flu antiviral drugs such as Tamiflu, as well as vaccines
– the two most important medical interventions for reducing
illness and deaths during a bird flu pandemic – will be inadequate
in all countries at the start of a pandemic and for many months thereafter.
Inadequate supplies of a bird flu vaccine is of particular concern,
as vaccines are considered the first line of defence for protecting
populations. On present trends, many developing countries will have
no access to vaccines throughout the duration of a bird flu pandemic.
7. Large numbers of deaths will occur
Historically, the number of deaths during a pandemic has varied greatly.
Death rates are largely determined by four factors: the number of
people who become infected, the virulence of the virus, the underlying
characteristics and vulnerability of affected populations, and the
effectiveness of preventive measures. Accurate predictions of mortality
cannot be made before the pandemic virus emerges and begins to spread.
All estimates of the number of deaths are purely speculative.
WHO has used a relatively conservative estimate – from 2 million
to 7.4 million deaths – because it provides a useful and plausible
planning target. This estimate is based on the comparatively mild
1957 pandemic. Estimates based on a more virulent virus, closer to
the one seen in 1918, have been made and are much higher. However,
the 1918 flu pandemic was considered exceptional.
8. Economic and social disruption will be great
High rates of illness and worker absenteeism are expected, and these
will contribute to social and economic disruption. Past pandemics
have spread globally in two and sometimes three waves. Not all parts
of the world or of a single country are expected to be severely affected
at the same time. Social and economic disruptions could be temporary,
but may be amplified in today’s closely interrelated and interdependent
systems of trade and commerce. Social disruption may be greatest when
rates of absenteeism impair essential services, such as power, transportation,
and communications. The affect of a bird flu outbreak on the stock markets of the world could therefore
be quite severe.
9. Every country must be prepared
WHO has issued a series of recommended strategic actions for responding
to the bird flu pandemic threat. The actions are designed to provide
different layers of defence that reflect the complexity of the evolving
situation. Recommended actions are different for the present phase
of pandemic alert, the emergence of a pandemic virus, and the declaration
of a pandemic and its subsequent international spread.
10. WHO will alert the world when the bird flu pandemic threat increases
WHO works closely with ministries of health and various public health
organizations to support countries' surveillance of circulating influenza
strains. A sensitive surveillance system that can detect emerging
influenza strains is essential for the rapid detection of a pandemic
virus.
Six distinct phases have been defined to facilitate pandemic preparedness
planning, with roles defined for governments, industry, and WHO. The
present situation is categorized as phase 3: a virus new to humans
is causing infections, but does not spread easily from one person
to another.
The World Health Organization (WHO)
has issued a new fact sheet on avian influenza, the first since the
disease moved out of Asia into Europe.
20 January 2006
The document summarizes the course of bird flu in its two-year spread
across Eurasia. In regard to the human cases that have appeared in
six nations, the fact sheet points out some puzzling unknown factors.
Human cases of disease have not appeared in commercial poultry enterprises
or culling operations, as might be expected. Instead, the majority
of cases have stricken previously healthy children and young adults
exposed to small flocks kept in domestic settings.
The document also describes physicians’ observations about
the “unusually aggressive clinical course” of the disease
in humans.
The fact sheet follows:
World Health Organization
[Geneva, Switzerland]
Avian influenza (" bird flu") - Fact Sheet
January 2006
The disease in birds
Avian influenza is an infectious disease of birds caused by type
A strains of the influenza virus. The disease occurs worldwide. While
all birds are thought to be susceptible to infection with avian influenza
viruses, many wild bird species carry these viruses with no apparent
signs of harm.
Other bird species, including domestic poultry, develop disease when
infected with avian influenza viruses. In poultry, the viruses cause
two distinctly different forms of disease – one common and mild,
the other rare and highly lethal. In the mild form, signs of illness
may be expressed only as ruffled feathers, reduced egg production,
or mild effects on the respiratory system. Outbreaks can be so mild
they escape detection unless regular testing for viruses is in place.
In contrast, the second and far less common highly pathogenic form
is difficult to miss. First identified in Italy in 1878, highly pathogenic
avian influenza is characterized by sudden onset of severe disease,
rapid contagion, and a mortality rate that can approach 100% within
48 hours. In this form of the disease, the virus not only affects
the respiratory tract, as in the mild form, but also invades multiple
organs and tissues. The resulting massive internal haemorrhaging has
earned it the lay name of “chicken Ebola”.
All 16 HA (haemagluttinin) and 9 NA (neuraminidase) subtypes of influenza
viruses are known to infect wild waterfowl, thus providing an extensive
reservoir of influenza viruses perpetually circulating in bird populations.
In wild birds, routine testing will nearly always find some influenza
viruses. The vast majority of these viruses cause no harm.
To date, all outbreaks of the highly pathogenic form of avian influenza
have been caused by viruses of the H5 and H7 subtypes. Highly pathogenic
viruses possess a tell-tale genetic “trade mark” or signature
– a distinctive set of basic amino acids in the cleavage site
of the HA – that distinguishes them from all other avian influenza
viruses and is associated with their exceptional virulence.
Not all virus strains of the H5 and H7 subtypes are highly pathogenic,
but most are thought to have the potential to become so. Recent research
has shown that H5 and H7 viruses of low pathogenicity can, after circulation
for sometimes short periods in a poultry population, mutate into highly
pathogenic viruses. Considerable circumstantial evidence has long
suggested that wild waterfowl introduce avian influenza viruses, in
their low pathogenic form, to poultry flocks, but do not carry or
directly spread highly pathogenic viruses. This role may, however,
have changed very recently: at least some species of migratory waterfowl
are now thought to be carrying the H5N1 virus in its highly pathogenic
form and introducing it to new geographical areas located along their
flight routes.
Apart from being highly contagious among poultry, avian influenza
viruses are readily transmitted from farm to farm by the movement
of live birds, people (especially when shoes and other clothing are
contaminated), and contaminated vehicles, equipment, feed, and cages.
Highly pathogenic viruses can survive for long periods in the environment,
especially when temperatures are low. For example, the highly pathogenic
H5N1 virus can survive in bird faeces for at least 35 days at low
temperature (4° C). At a much higher temperature (37° C),
H5N1 viruses have been shown to survive, in faecal samples, for six
days.
For highly pathogenic disease, the most important control measures
are rapid culling of all infected or exposed birds, proper disposal
of carcasses, the quarantining and rigorous disinfection of farms,
and the implementation of strict sanitary, or “biosecurity”,
measures. Restrictions on the movement of live poultry, both within
and between countries, are another important control measure. The
logistics of recommended control measures are most straightforward
when applied to large commercial farms, where birds are housed indoors,
usually under strictly controlled sanitary conditions, in large numbers.
Control is far more difficult under poultry production systems in
which most birds are raised in small backyard flocks scattered throughout
rural or periurban areas.
When culling – the first line of defence for containing outbreaks
– fails or proves impracticable, vaccination of poultry in a
high-risk area can be used as a supplementary emergency measure, provided
quality-assured vaccines are used and OIE recommendations are strictly
followed. The use of poor quality vaccines or vaccines that poorly
match the circulating virus strain may accelerate mutation of the
virus. Poor quality animal vaccines may also pose a risk for human
health, as they may allow infected birds to shed virus while still
appearing to be disease-free.
Apart from being difficult to control, outbreaks in backyard flocks
are associated with a heightened risk of human exposure and infection.
These birds usually roam freely as they scavenge for food and often
mingle with wild birds or share water sources with them. Such situations
create abundant opportunities for human exposure to the virus, especially
when birds enter households or are brought into households during
adverse weather, or when they share areas where children play or sleep.
Poverty exacerbates the problem: in situations where a prime source
of food and income cannot be wasted, households frequently consume
poultry when deaths or signs of illness appear in flocks. This practice
carries a high risk of exposure to the virus during slaughtering,
defeathering, butchering, and preparation of poultry meat for cooking,
but has proved difficult to change. Moreover, as deaths of birds in
backyard flocks are common, especially under adverse weather conditions,
owners may not interpret deaths or signs of illness in a flock as
a signal of avian influenza and a reason to alert the authorities.
This tendency may help explain why outbreaks in some rural areas have
smouldered undetected for months. The frequent absence of compensation
to farmers for destroyed birds further works against the spontaneous
reporting of outbreaks and may encourage owners to hide their birds
during culling operations.
The role of migratory birds
During 2005, an additional and significant source of international
spread of the virus in birds became apparent for the first time, but
remains poorly understood. Scientists are increasingly convinced that
at least some migratory waterfowl are now carrying the H5N1 virus
in its highly pathogenic form, sometimes over long distances, and
introducing the virus to poultry flocks in areas that lie along their
migratory routes. Should this new role of migratory birds be scientifically
confirmed, it will mark a change in a long-standing stable relationship
between the H5N1 virus and its natural wild-bird reservoir.
Evidence supporting this altered role began to emerge in mid-2005
and has since been strengthened. The die-off of more than 6000 migratory
birds, infected with the highly pathogenic H5N1 virus, that began
at the Qinghai Lake nature reserve in central China in late April
2005, was highly unusual and probably unprecedented. Prior to that
event, wild bird deaths from highly pathogenic avian influenza viruses
were rare, usually occurring as isolated cases found within the flight
distance of a poultry outbreak. Scientific studies comparing viruses
from different outbreaks in birds have found that viruses from the
most recently affected countries, all of which lie along migratory
routes, are almost identical to viruses recovered from dead migratory
birds at Qinghai Lake. Viruses from Turkey’s first two human
cases, which were fatal, were also virtually identical to viruses
from Qinghai Lake.
Countries affected by outbreaks in birds
The outbreaks of highly pathogenic avian influenza that began in
south-east Asia in mid-2003 and have now spread to a few parts of
Europe, are the largest and most severe on record. To date, nine Asian
countries have reported outbreaks (listed in order of reporting):
the Republic of Korea, Viet Nam, Japan, Thailand, Cambodia, the Lao
People’s Democratic Republic, Indonesia, China, and Malaysia.
Of these, Japan, the Republic of Korea, and Malaysia have controlled
their outbreaks and are now considered free of the disease. Elsewhere
in Asia, the virus has become endemic in several of the initially
affected countries.
In late July 2005, the virus spread geographically beyond its original
focus in Asia to affect poultry and wild birds in the Russian Federation
and adjacent parts of Kazakhstan. Almost simultaneously, Mongolia
reported detection of the highly pathogenic virus in wild birds. In
October 2005, the virus was reported in Turkey, Romania, and Croatia.
In early December 2005, Ukraine reported its first outbreak in domestic
birds. Most of these newer outbreaks were detected and reported quickly.
Further spread of the virus along the migratory routes of wild waterfowl
is, however, anticipated. Moreover, bird migration is a recurring
event. Countries that lie along the flight pathways of birds migrating
from central Asia may face a persistent risk of introduction or re-introduction
of the virus to domestic poultry flocks.
Prior to the present situation, outbreaks of highly pathogenic avian
influenza in poultry were considered rare. Excluding the current outbreaks
caused by the H5N1 virus, only 24 outbreaks of highly pathogenic avian
influenza have been recorded worldwide since 1959. Of these, 14 occurred
in the past decade. The majority have shown limited geographical spread,
a few remained confined to a single farm or flock, and only one spread
internationally. All of the larger outbreaks were costly for the agricultural
sector and difficult to control.
The disease in humans
History and epidemiology. Influenza viruses are normally highly species-specific,
meaning that viruses that infect an individual species (humans, certain
species of birds, pigs, horses, and seals) stay “true”
to that species, and only rarely spill over to cause infection in
other species. Since 1959, instances of human infection with an avian
influenza virus have occurred on only 10 occasions. Of the hundreds
of strains of avian influenza A viruses, only four are known to have
caused human infections: H5N1, H7N3, H7N7, and H9N2. In general, human
infection with these viruses has resulted in mild symptoms and very
little severe illness, with one notable exception: the highly pathogenic
H5N1 virus.
Of all influenza viruses that circulate in birds, the H5N1 virus
is of greatest present concern for human health for two main reasons.
First, the H5N1 virus has caused by far the greatest number of human
cases of very severe disease and the greatest number of deaths. It
has crossed the species barrier to infect humans on at least three
occasions in recent years: in Hong Kong in 1997 (18 cases with six
deaths), in Hong Kong in 2003 (two cases with one death) and in the
current outbreaks that began in December 2003 and were first recognized
in January 2004.
A second implication for human health, of far greater concern, is
the risk that the H5N1 virus – if given enough opportunities
– will develop the characteristics it needs to start another
influenza pandemic. The virus has met all prerequisites for the start
of a pandemic save one: an ability to spread efficiently and sustainably
among humans. While H5N1 is presently the virus of greatest concern,
the possibility that other avian influenza viruses, known to infect
humans, might cause a pandemic cannot be ruled out.
During the first documented outbreak of human infections with H5N1,
which occurred in Hong Kong in 1997, the 18 human cases coincided
with an outbreak of highly pathogenic avian influenza, caused by a
virtually identical virus, in poultry farms and live markets. Extensive
studies of the human cases determined that direct contact with diseased
poultry was the source of infection. Studies carried out in family
members and social contacts of patients, health workers engaged in
their care, and poultry cullers found very limited, if any, evidence
of spread of the virus from one person to another. Human infections
ceased following the rapid destruction – within three days –
of Hong Kong’s entire poultry population, estimated at around
1.5 million birds. Some experts believe that that drastic action may
have averted a pandemic.
All evidence to date indicates that close contact with dead or sick
birds is the principal source of human infection with the H5N1 virus.
Especially risky behaviours identified include the slaughtering, defeathering,
butchering and preparation for consumption of infected birds. In a
few cases, exposure to chicken faeces when children played in an area
frequented by free-ranging poultry is thought to have been the source
of infection. Swimming in water bodies where the carcasses of dead
infected birds have been discarded or which may have been contaminated
by faeces from infected ducks or other birds might be another source
of exposure. In some cases, investigations have been unable to identify
a plausible exposure source, suggesting that some as yet unknown environmental
factor, involving contamination with the virus, may be implicated
in a small number of cases. Some explanations that have been put forward
include a possible role of peri-domestic birds, such as pigeons, or
the use of untreated bird faeces as fertilizer.
At present, H5N1 avian influenza remains largely a disease of birds.
The species barrier is significant: the virus does not easily cross
from birds to infect humans. Despite the infection of tens of millions
of poultry over large geographical areas for more than two years,
fewer than 200 human cases have been laboratory confirmed. For unknown
reasons, most cases have occurred in rural and periurban households
where small flocks of poultry are kept. Again for unknown reasons,
very few cases have been detected in presumed high-risk groups, such
as commercial poultry workers, workers at live poultry markets, cullers,
veterinarians, and health staff caring for patients without adequate
protective equipment. Also lacking is an explanation for the puzzling
concentration of cases in previously healthy children and young adults.
Research is urgently needed to better define the exposure circumstances,
behaviours, and possible genetic or immunological factors that might
enhance the likelihood of human infection.
Assessment of possible cases. Investigations of all the most recently
confirmed human cases, in China, Indonesia, and Turkey, have identified
direct contact with infected birds as the most likely source of exposure.
When assessing possible cases, the level of clinical suspicion should
be heightened for persons showing influenza-like illness, especially
with fever and symptoms in the lower respiratory tract, who have a
history of close contact with birds in an area where confirmed outbreaks
of highly pathogenic H5N1 avian influenza are occurring. Exposure
to an environment that may have been contaminated by faeces from infected
birds is a second, though less common, source of human infection.
To date, not all human cases have arisen from exposure to dead or
visibly ill domestic birds. Research published in 2005 has shown that
domestic ducks can excrete large quantities of highly pathogenic virus
without showing signs of illness. A history of poultry consumption
in an affected country is not a risk factor, provided the food was
thoroughly cooked and the person was not involved in food preparation.
As no efficient human-to-human transmission of the virus is known
to be occurring anywhere, simply travelling to a country with ongoing
outbreaks in poultry or sporadic human cases does not place a traveller
at enhanced risk of infection, provided the person did not visit live
or “wet” poultry markets, farms, or other environments
where exposure to diseased birds may have occurred.
Clinical features (1) In many patients, the disease caused by the
H5N1 virus follows an unusually aggressive clinical course, with rapid
deterioration and high fatality. Like most emerging disease, H5N1
influenza in humans is poorly understood. Clinical data from cases
in 1997 and the current outbreak are beginning to provide a picture
of the clinical features of disease, but much remains to be learned.
Moreover, the current picture could change given the propensity of
this virus to mutate rapidly and unpredictably.
The incubation period for H5N1 avian influenza may be longer than
that for normal seasonal influenza, which is around 2 to 3 days. Current
data for H5N1 infection indicate an incubation period ranging from
2 to 8 days and possibly as long as 17 days. However, the possibility
of multiple exposure to the virus makes it difficult to define the
incubation period precisely. WHO currently recommends that an incubation
period of 7 days be used for field investigations and the monitoring
of patient contacts.
Initial symptoms include a high fever, usually with a temperature
higher than 38oC, and influenza-like symptoms. Diarrhoea, vomiting,
abdominal pain, chest pain, and bleeding from the nose and gums have
also been reported as early symptoms in some patients.
Watery diarrhoea without blood appears to be more common in H5N1
avian influenza than in normal seasonal influenza. The spectrum of
clinical symptoms may, however, be broader, and not all confirmed
patients have presented with respiratory symptoms. In two patients
from southern Viet Nam, the clinical diagnosis was acute encephalitis;
neither patient had respiratory symptoms at presentation. In another
case, from Thailand, the patient presented with fever and diarrhoea,
but no respiratory symptoms. All three patients had a recent history
of direct exposure to infected poultry.
One feature seen in many patients is the development of manifestations
in the lower respiratory tract early in the illness. Many patients
have symptoms in the lower respiratory tract when they first seek
treatment. On present evidence, difficulty in breathing develops around
5 days following the first symptoms. Respiratory distress, a hoarse
voice, and a crackling sound when inhaling are commonly seen. Sputum
production is variable and sometimes bloody. Most recently, blood-tinted
respiratory secretions have been observed in Turkey. Almost all patients
develop pneumonia. During the Hong Kong outbreak, all severely ill
patients had primary viral pneumonia, which did not respond to antibiotics.
Limited data on patients in the current outbreak indicate the presence
of a primary viral pneumonia in H5N1, usually without microbiological
evidence of bacterial supra-infection at presentation. Turkish clinicians
have also reported pneumonia as a consistent feature in severe cases;
as elsewhere, these patients did not respond to treatment with antibiotics.
In patients infected with the H5N1 virus, clinical deterioration
is rapid. In Thailand, the time between onset of illness to the development
of acute respiratory distress was around 6 days, with a range of 4
to 13 days. In severe cases in Turkey, clinicians have observed respiratory
failure 3 to 5 days after symptom onset. Another common feature is
multiorgan dysfunction, notably involving the kidney and heart. Common
laboratory abnormalities include lymphopenia, leukopenia, elevated
aminotransferases, and mild-to-moderate thrombocytopenia with some
instances of disseminated intravascular coagulation.
Limited evidence suggests that some antiviral drugs, notably oseltamivir
(commercially known as Tamiflu), can reduce the duration of viral
replication and improve prospects of survival, provided they are administered
within 48 hours following symptom onset. However, prior to the outbreak
in Turkey, most patients have been detected and treated late in the
course of illness. For this reason, clinical data on the effectiveness
of oseltamivir are limited. Moreover, oseltamivir and other antiviral
drugs were developed for the treatment and prophylaxis of seasonal
influenza, which is a less severe disease associated with less prolonged
viral replication. Recommendations on the optimum dose and duration
of treatment for H5N1 avian influenza, also in children, need to undergo
urgent review, and this is being undertaken by WHO.
In suspected cases, oseltamivir should be prescribed as soon as possible
(ideally, within 48 hours following symptom onset) to maximize its
therapeutic benefits. However, given the significant mortality currently
associated with H5N1 infection and evidence of prolonged viral replication
in this disease, administration of the drug should also be considered
in patients presenting later in the course of illness.
Currently recommended doses of oseltamivir for the treatment of influenza
are contained in the product information at the manufacturer’s
web site. The recommended dose of oseltamivir for the treatment of
influenza, in adults and adolescents 13 years of age and older, is
150 mg per day, given as 75 mg twice a day for 5 days. Oseltamivir
is not indicated for the treatment of children younger than 1 year
of age.
As the duration of viral replication may be prolonged in cases of
H5N1 infection, clinicians should consider increasing the duration
of treatment to 7 to 10 days in patients who are not showing a clinical
response. In cases of severe infection with the H5N1 virus, clinicians
may need to consider increasing the recommended daily dose or the
duration of treatment, keeping in mind that doses above 300 mg per
day are associated with increased side effects. For all treated patients,
consideration should be given to taking serial clinical samples for
later assay to monitor changes in viral load, to assess drug susceptibility,
and to assess drug levels. These samples should be taken only in the
presence of appropriate measures for infection control.
In severely ill H5N1 patients or in H5N1 patients with severe gastrointestinal
symptoms, drug absorption may be impaired. This possibility should
be considered when managing these patients.
Countries with human cases in the outbreak
To date, human cases have been reported in six countries, most of
which are in Asia: Cambodia,
China,
Indonesia,
Thailand,
Turkey,
and Viet
Nam. The first patients in the current outbreak, which
were reported from Viet Nam, developed symptoms in December 2003 but
were not confirmed as H5N1 infection until 11 January 2004. Thailand
reported its first cases on 23 January 2004. The first case in Cambodia
was reported on 2 February 2005. The next country to report cases
was Indonesia, which confirmed its first infection on 21 July. China’s
first two cases were reported on 16 November 2005. Confirmation of
the first cases in Turkey came on 5 January 2006. All human cases
have coincided with outbreaks of highly pathogenic H5N1 avian influenza
in poultry. To date, Viet Nam has been the most severely affected
country, with more than 90 cases.
Altogether, more than half of the laboratory-confirmed cases have
been fatal. H5N1 avian influenza in humans is still a rare disease,
but a severe one that must be closely watched and studied, particularly
because of the potential this virus to evolve in ways that could start
a pandemic.
(1) This section has been reviewed by a virtual network of clinicians
experienced in the treatment of H5N1 infections and other severe respiratory
diseases. The network was convened for the first time on 16 January
2006. Physicians from Yüzüncü Yil University, Faculty
of Medicine, Van, Turkey participated in the exchange of information
and experiences. Other institutions represented include the University
of Hong Kong (China); the Hospital for Tropical Diseases, Ho Chi Minh
City (Viet Nam); and the University of Virginia, Charlottesville,
Virginia (USA).
(end fact sheet)
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