Avian influenza, human (146): South Korea, asymptomatic

International Society for Infectious Diseases
<http://www.isid.org>

[1]
Source: Yonhap News online [edited]
< http://english.yna.co.kr/Engnews/20060915/460100000020060915113519E7.html>


South Korea's disease control agency confirmed on Fri [15 Sep 2006]
that 5 people have developed antibodies to the lethal H5N1 strain of
bird flu after taking part in the slaughtering and disposal of
infected chickens and ducks [in 2003 -- see below. - Mod.JW].

The 5 people tested positive for bird flu antibodies, but none of
them [had] shown symptoms of the disease as defined by the World
Health Organization (WHO), the Korea Center for Disease Control and
Prevention stated.


******
[2]
Source: Agence France Presse, Fri 15 Sep 2006 [edited]
< http://www.afp.com/english/home/>

Health officials were cited as saying [on Fri 15 Sep 2006] that 5
South Koreans were infected by the H5N1 bird flu virus 2 years ago
while helping slaughter birds that had contracted the disease. The
five were exposed to the virus between late 2003 and early 2004 but
have shown no symptoms, said the Center for Disease Control and
Prevention of the Health Ministry.

They make up only the 2nd known incident of human infection in South
Korea, which slaughtered 5.3 million poultry during a bird flu
epidemic 2 years ago.

At the time, more than 2100 people who had helped with the
destruction of the birds were tested for the virus [with negative
results. - Mod.JW].

******
[3]
Source: Reuters Foundation AlertNet, Fri 15 Sep 2006 [edited]
<http://www.alertnet.org/thenews/newsdesk/SEO196446.htm>

Five more South Koreans were infected with the H5N1 bird flu virus
about 3 years ago but none of them developed any serious illnesses,
officials said on Fri [15 Sep 2006] after recently completed testing
on old samples.

First batch
--------
South Korea, which did not have comprehensive testing at the time,
sent samples of 318 poultry industry workers taken during an outbreak
in late 2003 and early 2004 to the U.S. Centers for Disease Control
and Prevention in 2005 for further examination. Of those workers, 4
South Koreans were infected, the CDC has said. The government said in
February [2006] the 4 did not develop major illnesses.

2nd batch
---------
The results prompted South Korean health officials to send samples to
the CDC from another 2109 people and of these, 5 were also infected,
the health agency said on Friday [15 Sep 2006]. "The 5 did not
develop major illnesses and have no strain to transmit bird flu," the
Korea Centre for Disease Control and Prevention said in a statement.

About 400 000 poultry at South Korean farms were infected by bird flu
between December 2003 and March 2004, but no human cases were
reported at that time. All of the samples sent by South Korea to the
United States were from people involved in the culling of about 5
million poultry. There have been no reported cases of bird flu in
South Korea since the 2003-2004 outbreak.

The World Health Organisation said on Thursday 2 cases in Indonesia
had been recognised retroactively, including one where human-to-human
transmission could not be ruled out. The latest number of cases
globally stands at 246 since 2003, not including the South Korean
cases, with 144 deaths.

Retrospective analysis has established that beginning mid-2003 HPAI
H5N1 virus began to cause outbreaks of poultry disease in Asia which
were unrecognized at that time. In December 2003, 2 tigers and 2
leopards in a Thai zoo died as a result of consuming H5N1-infected
chicken carcasses. Later in the same month South Korea confirmed that
HPAI H5N1 virus infection was the cause of poultry deaths at 3 farms.
In early 2004 H5N1 virus infection was reported from Viet Nam, Japan,
and Thailand. The 1st laboratory-confirmed cases of H5N1 human
infection were reported in Thailand and later sporadically throughout
East Asia (all symptomatic). Just as in Hong Kong in 1997, the
outbreaks in South Korea and Japan were rapidly contained and
eradicated by a combination of early detection, extensive culling,
and continued surveillance. H5N1 virus infection has not recurred in
South Korea. No human cases of infection were reported at that time,
but later a small number of those involved in poultry culling
experienced asymptomatic infection and developed immune responses.
The above reports add another 5 asymptomatic cases bringing the total to 9.

The virus responsible for the outbreaks in South Korea and Japan
belonged to the V genotype of H5N1 avian influenza virus, whereas the
predominant virus in East Asia belongs to the Z genotype. These
genotypes are reassortants which differ in the origin of their NA
genome subunit. It has not been established if this is relevant to
the apparent lack of virulence of the South Korean virus.