Posted by
Nancy Nurse on Tuesday, September 26, 2006 7:38:59 AM
Avian flu 'may strike' in winter Top
influenza scientists warned on Friday of the big possibility of a major
bird flu outbreak in China this winter or next spring.
Such an
outbreak, which would hit poultry and human beings, would probably take
place as common flu cases reach their peak, said Zeng Guang, chief
epidemiology scientist at China's Centre for Disease Control and
Prevention.
Zeng said that the three major bird flu outbreaks over the past three years had all taken place during the winter or spring.
Great
attention must be paid to the possible occurrence of common flu and
bird flu peaks at the same time, Zeng told a forum jointly held by
Sanofi Pasteur and the Chinese Preventive Medicine Association in
Beijing.
It remains difficult to determine how the H5N1 virus
will develop, said Zeng, but he noted there was a possibility it may
form a hybrid with other flu viruses.
Possible crossbreeding may result in a new form of virus which could be transmitted between humans, he noted.
Currently,
all human cases of bird flu have been infected by sick birds. There is
no evidence to suggest that the virus can be passed from person to
person, according to World Health Organization (WHO).
WHO
experts have repeatedly warned there is a major risk that the bird flu
virus may be transmitted between humans, which would result in a global
pandemic.
Zeng said that the three flu pandemics over the past century were all caused by a hybrid virus.
Flu pandemics generally take place three or four times per century.
The last major pandemic took place in 1918-1919 and killed an estimated 40-50 million people across the globe.
Flu
viruses can be divided into three groups A, B and C. Only A, which
infects many animal species such as birds and swine, and B, which only
affects humans, can cause severe disease and lead to epidemics.
Bird flu is an infectious disease caused by A viruses.
Highly
pathogenic bird flu, such as that caused by the H5N1 strain currently
circulating in Asia and other parts of the world, is characterized by
its sudden onset, severe illness, and generally quick death.
The
H5N1 strain is of particular concern because it mutates rapidly and can
acquire genes from viruses infecting other animal species. This highly
pathogenic strain is now known to cause severe disease and death in
humans.
As the disease increases among birds and humans, the
likelihood also increases that a human concurrently infected with human
and bird flu strains will serve as the "mixing vessel" for a new
influenza subtype that can be transmitted easily from person to person,
thus sparking a flu pandemic, according to the WHO.
At present,
there remains one prerequisite for the start of a pandemic that the
current H5N1 virus has yet to meet sustained and efficient transmission
among humans.
Currently, about 250,000 to 300,000 people die
across the globe every year as a result of complications caused by
various types of influenza, he said.
In this regard, it is vital to prevent common influenza in the war against a possible bird flu epidemic or pandemic, he added.
In China, around 130 million people are infected with influenza every year.
From
November 2003 to September 14 this year, a total of 246 people had been
infected by H5N1 in 10 countries, resulting in 144 fatalities. A total
of 21 people in China have been infected by the virus, with 14 losing
their lives.
Evidence to date indicates that close contact with
sick or dead birds, such as slaughtering or de-feathering, is the
principal source of infection.
Worldwide, about a dozen companies are currently conducting clinical trials on bird flu vaccines.
As
scientists still do not know enough about the virus, public education
is an important way to prevent a bird flu outbreak, said Zhang Bin, an
official from the Ministry of Health.
Source: China Daily