Top influenza scientists warned on Friday of the big possibility
of a major bird flu outbreak in China this winter or next
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
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
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
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
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
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.
(China Daily September 23, 2006)