Published Date: 2005-08-02 23:50:00
Subject: PRO/AH/EDR> Streptococcus suis, porcine, human - China (03)
Archive Number: 20050802.2246
STREPTOCOCCUS SUIS, PORCINE, HUMAN - CHINA (03)
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Transactions of the Royal Society of Tropical Medicine and Hygiene
Date: Tue 2 Aug 2005
From: Mary Marshall <email@example.com>
Source: New Scientist, 1 Aug 2005 [edited]
Pig disease may be spreading between humans
Vaccines to combat a deadly pig-borne disease were flown to
south-western China on Sunday [31 Aug 2005], where the spread of the
rare illness has already killed 36 people and infected 198. The
unusually high numbers of people infected by the swine disease has
led scientists to speculate that it may be being spread from
human-to-human or that another disease entirely is to blame.
_Streptococcus suis_ type II, although relatively common in swine,
spreads to humans extremely rarely, and the size and virulence of
this current outbreak, in the province of Sichuan, has taken the
World Health Organization by surprise.
The Chinese government responded on Sunday [31 Aug 2005] by
airlifting the 1st batch of a vaccine for the infection -- enough to
treat 360 000 pigs -- from the southern city of Guangzhou to the
affected towns. The vaccine's manufacturers say they will be
producing enough vaccine to treat 10 million pigs in the coming days,
but vaccines take 3 weeks to produce immunity in the pigs.
Health authorities in the province have distributed 2 million notices
to educate poor, often illiterate farmers and their children not to
slaughter pigs or eat their meat. 39 temporary roadside quarantine
stations have been set up to prevent dead pigs from reaching markets;
they will be burned instead.
China's state-controlled media says the government has brought the
disease under control and that no human-to-human transmission of
infection has been found. But there has been widespread criticism of
the way the situation has been handled, with parallels being drawn to
China's handling of SARS (severe acute respiratory syndrome) and bird
flu outbreaks. The authorities knew of the 1st human cases on 24 Jun
2005, but it only allowed the news out on 25 Jul 2005. And China has
banned local and foreign reporters from entering the region.
The secrecy has bred suspicion elsewhere. The WHO has said that it is
baffled, because _S. suis_ has never affected so many people in an
outbreak before; it usually just infects one or 2 people at a time.
And when people have been infected previously, mortality rates have
been below 10 percent, and different symptoms have been exhibited.
"It could be another disease altogether, it need not be
_Streptococcus suis_, because the presentation is so atypical,"
Samson Wong, a microbiologist at the University of Hong Kong, told
Reuters. "In past literature, there have been one or 2 cases when
people died within 36 hours, but those were exceptions rather than
the rule. The deaths in China are very unusual."
Wong also says many patients in Sichuan were bleeding under the skin,
a symptom that has been cited in only 2 or 3 cases in medical
literature on the infection, and that deafness, which is commonly
found with the disease, has been little mentioned in the outbreak.
Experts quoted in other news reports have also said that the swine
bacterium is an unlikely cause, with the symptoms, widespread
geography of those affected and the speed of infection pointing to a
Other experts question China's denial of human-to-human spread. "The
organism is carried on the pig's tonsils and is spread pig-to-pig
through nose rubbing or coughing. But it's only found in small
concentration on the pigs' tonsils, so it's difficult for a human to
catch it that way," says Jill Thompson from the UK's Veterinary
Investigation Centre in Edinburgh.
"When the infection spreads to the brain, causing meningitis, it's in
far greater concentration, and so it can be transmitted to humans who
eat raw infected pork or handle the dead animal with open cuts," she
told New Scientist.
"It is so rare for humans to become infected, most farm workers
develop some immunity from the endemic disease. What might have
happened is that the bacteria have acquired virulence factors from
another organism -- a bacterium or virus that might be harmless --
and the combined virulence factors have turned it into a superbug,
which could be transmitted human-to-human through coughing," she
Andrew Rycroft, a microbiologist from the Royal Veterinary College in
Hertfordshire, UK agrees. "The likelihood is that once it gets
established in the human respiratory tract, it can be transmitted by
the respiratory tract between humans very much more quickly," he
says, citing an analogy between the bubonic plague, which soon became
the far more virulent pneumonic plague when it was transmitted by the
human respiratory system.
[Byline: Gaia Vice]
Date: Tue 2 Aug 2005
From: ProMED-mail <firstname.lastname@example.org>
Source: Reuters news alert, 2 Aug 2005 [edited]
China farmers ignore swine flu hygiene orders
Many frugal farmers in southwest China are refusing to bury infected
pigs safely, Chinese media said on Tuesday [2 Aug 2005], raising
fears that a deadly swine flu could spread further, after infecting
almost 200 people and killing 36.
Draconian measures were in place around the Chinese capital to
prevent infection. The Beijing News said city authorities had blocked
inward shipments of about 4000 tons of pork and pork products from
stricken Sichuan province *****up to 31 Jul 2005.
Many impoverished Sichuan farmers, having already bought piglets,
inoculation and feed, are refusing to spend more on burying sick pigs
with disinfectant. Instead, they slaughter them and eat the meat
"Households are not following guidelines in dealing with sick and
dead pigs to prevent possible harm," the Beijing News said.
Asked whether her family had followed government orders to dispose of
their sick pigs, the wife of a farmer in Sichuan's hard-hit Zizhong
county reportedly told state television: "At any rate, we didn't eat
Zizhong health worker Wen Youhai had admitted to simply taking
farmers at their word that they had properly handled sick pigs rather
than observing burials in person, the daily said.
The Health Ministry Web site, in its latest bulletin, said 2 deaths
and 17 infections with pig-borne bacteria _Streptococcus suis_ had
been reported between Sunday [31 Jul 2005] and midday Monday [1 Aug
2005] in Sichuan.
Health officials insist the outbreak is under control and that the
latest victims represented previously undiagnosed cases, not new
cases which would indicate the disease was spreading.
A total of 198 people in 108 villages and townships in Sichuan had
contracted the disease, apparently from slaughtering, handling or
eating infected pigs, the ministry said.
The official China Youth Daily published a picture of a stall owner
in Ziyang city, where the disease was 1st reported in June 2005,
selling pork at a traditional market. The headline read: "Ziyang
residents dare to sell pork again."
In one unconfirmed report, the Chongqing Evening News said last week
[final week July 2005] an unscrupulous meat dealer had dug up sick
and dead pigs he was forced by police to bury a day earlier and sold
the meat in a nearby town for a big profit.
Sichuan has launched a campaign to educate illiterate farmers and
their children not to slaughter or eat sick pigs.
The government has also vowed to punish officials caught covering up
or delaying reports on infections. 2 officials and one health
inspector have already been fired for negligence.
While most of the infections have been found in Sichuan, cases have
also been reported in Guangdong province and neighboring Hong Kong.
Shipments of pork from Sichuan, China's top producer, to Hong Kong
have been stopped, and the city has stepped up inspections and
quarantine procedures on all live pigs and frozen pork imported from
Hong Kong health experts have confirmed the bacteria as
_Streptococcus suis_ and found no evidence of any mutation, the South
China Morning Post said.
In addition to Beijing, other Chinese cities have also set up tight
perimeter checks to block pork from Sichuan.
[_Streptococcus suis_ is the causative agent of a wide range of
infections in pigs, including meningitis, arthritis, pneumonia,
septicemia, endocarditis, encephalitis, polyserositis, and abscesses.
The bacterium is endemic in all pig-raising countries world-wide,
especially affecting large, intensively managed pig farms. The
disease is not regarded to be highly infectious, most outbreaks are
limited to the affected farms, and is not notifiable, nationally or
internationally. Nevertheless, in the affected farms, significant
economic losses may be observed, and, since antibiotic therapy gives
unsatisfactory results, vaccines have been developed and widely used.
The results of vaccination have been inconsistent.
Human infection may occur, but it has generally been known as
occupational, affecting farmers and personnel engaged with pig
breeding and their handling, including slaughter, not a food-borne
The current spread of _Streptococcus suis_ in China seems odd.
Something must be perturbing the usual epidemiology of this
occupational infection. There may be several guesses (and I emphasize
guesses at this point) based on the rereading of the reports:
1) The disease is being spread by the foodborne route, and,
therefore, is being transported to markets at substantial distances.
This would probably be associated with some clinical outbreak in
swine in Sichuan, while sick pigs -- instead of being presented for
slaughter -- are sold on the open market at heavily discounted
prices. As knowledge of the outbreak in people dries up the local
market, unscrupulous dealers would send the meat further afield, thus
explaining the new cities involved. The farmer eating his own sick
pig falls in this category as well. The articles above, and many
others, refer incorrectly to this disease as swine flu. Swine
influenza is a well known disease but it caused by the influenza
virus, not _Streptococcus suis_.
2) There might be a co-infection with a virus that weakens certain
human immune systems in the outbreak area and, therefore, allows
opportunistic _Streptococcus suis_ infection. What virus can only be
3) There might be a synergism between 2 pathogens, say a virus and
_Streptococcus suis_ . If the latter was occult and widespread in a
latent form, it is just adding a match to tinder.
4) The old epidemiological adage: seek and ye shall find. This is
more applicable to the newer cases and rather doubtful if
representing the explanation for the outbreak in Sichuan.
Unfortunately, there is little information on the swine populations
in Sichuan, because one key factor in putting together the cause of
the outbreak would be to know the status of local swine farms where
the cases are occurring. There is little information, other than bans
on pork, coming from the animal side, but unless there is evidence of
an outbreak in pigs indicating a new, more virulent strain,
occupational exposure to normal _Streptococcus suis_ could hardly
explain the magnitude of the cases in humans generated this far. -
Mods.PC, MHJ, TG, AS]
[Additionally, the organism could have acquired a toxin or some other
factor, increasing its virulence. To date, it has not clearly been
spread from human to human, and the speculation of an analogy to
pneumonic plague and its transmissibility is just that. - Mod.LL]