Anxiety: Human-to-human bird flu infection in China

Published 10 April 2008

A 24-year old man in China probably infected his father with the H5N1 strain of bird flu before dying, renewing concerns that the disease may soon spread easily among humans

If bird flu could spread from human to human, the making of a
major epidemic would be afoot. The news from China about human-to-human
infection, therefore, is not good. The case is one of a handful during the last
four years in which the H5N1 virus is suspected to have spread from one person
to another, according to lead researcher Yu Wang of the Chinese Centre for
Disease Control. To date, however, all such cases have been what scientists
call “limited, non-sustained, person-to-person transmission,” meaning
that contagion only occurs under very specific circumstances. The vast majority
of the known 378 human cases of H5N1 bird flu since 2003 were spread by
domestic or wild fowl, according to the World Health Organisation (WHO). More
than 60 percent proved fatal. “It is not normal social contact that has
led to the human transmission,” epidemiologist Jeremy Farrar, a researcher
at the national Institute of Hygiene and Epidemiology, told AFP in an interview. “In this case it took extensive
exposure to secretions of somebody who was very sick in hospital,” he
explained. Another limiting factor may be genetic, the study found. The
suspected cases of human-to-human transmission have all been “within the
family, among blood relatives,” said Farrar.

None of the 91 persons besides the
father who came into contact with his son before he died showed any sign of
infection, said the study, published in the British medical weekly The
. Nor was there any significant genetic variation between the viral
strain in the father or the son. Experts fear that the H5N1 virus could mutate
after infecting one human into a more contagious form, as occurred during at
least three flu pandemics in the twentieth century. An estimated 20 to 40
million people perished in the so-called “Spanish flu” of 1918. Any
new clusters of the virus “require urgent investigation because of the
possibility that a change in the epidemiology of H5N1 cases could indicate that
H5N1 viruses have acquired the ability to spread more easily among people,”
said Wang. The two cases examined in the study were identified in December in
the city of Nanjing, in China’s Jiangsu Province. Since 2003, there
have been 107 H5N1 bird flu fatalities in Indonesia, 52 in Vietnam, 20 in China, 17 in Thailand, and between one and
seven in seven other nations.