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With the discovery of bird flu among fowl in an aviary in eastern Seoul, South Korea this week, citizens are now worried about contact with one of the denizens of their capital city; the ubiquitous pigeon.
While some officials have claimed that pigeons are practically immune to the H5N1 virus, there are anecdotal reports, and a few scientific studies, to suggest otherwise.
First the story from the Korea Times, then some background information.
Pigeons Strike Fear Into Citizens
A major bird market in Dongdaemun, Seoul is deserted Thursday afternoon after virulent H5N1 strain of avian influenza was detected in the capital./ Yonhap
By Bae Ji-sook
Staff Reporter
``Are these pigeons safe?'' Citizens express fear towards pigeons and magpies on the streets after dead birds found at an aviary in Gwangjin, eastern Seoul, were confirmed to have the H5N1 strain of the bird flu virus that can be deadly to humans.
At parks, plazas or apartment complexes where birds flock, pedestrians dodge the menacing birds like something out of Hitchcock's movie - The Birds. Some people cover their nose or eyes and a few even wanted to slaughter them all.
``This morning I told the kids never to touch the birds nor feed them,'' said a 68-year-old woman who took her kid to Boramae Park in Seoul, Thursday. ``You get very cautious after hearing that the bird flu may be just around the corner.''
At Seoul Station plaza, where hundreds of pigeons live and walk around, people tried to keep their distance, bracing themselves against walls if one came too close. A citizen said, ``Let's just get rid of all the pigeons like we killed chickens or ducks if there was the slightest possibility of them carrying the disease.''
Local public health offices are receiving hundreds of phone calls from people asking about the precise symptoms of bird flu and saying they might have caught it. Especially those who had visited the children's park next to the aviary, who complained of soar throats, high fever and other ailments. ``Many of them just had cold,''' a staff member at the office said.
The government set out several measures to ease people's anxiety. They have shut down the aviary and given only limited access to the children's park and traditional open market where the dead pheasants were sold. Quarantine officials and volunteers also tried to isolate 40 birds in Ilgam Pond inside Konkuk University, right next to the aviary.
It has also been decided that the zoo inside Seoul Grand Park in Gwacheon will be shut down should a case of bird flu be reported within three kilometers.
The government has begun informing people of the avian influenza. ``Experts say the virus could be carried in the air, but it does not mean all surrounding air contains the virus,'' a city government spokesman said.
It also told citizens to refrain from touching birds at parks or ponds in the neighborhood.
The spokesman asked parents to take extra care of their children. ``There are chicks sold in front of elementary school front gates. We know many children want to buy or touch them because they look cute. But they may touch their excrement, the most likely thing to contain contagious materials,'' he said.
Prof. Kim Jae-hong of Seoul National University said there is little chance people will get infected by such a virus by simply passing by them or being in the same open area. ``I think the reason there were cases of human contraction in Southeast Asian countries such as Vietnam is because their culture is to breed such animals indoors and therefore they get in contact with their excrement easily,'' he said.
I've written about the fear that pigeons might be vectors for the bird flu virus several times, including in The Origins Of The Feces in December of 2006, and a year later in The Latest Poop On Pigeons.
Around the world, opinions vary over the threat these city dwellers present. In Bangladesh pigeons, along with ducks and chickens, are routinely culled in their fight against bird flu. While in Saudi Arabia, they claim that pigeons are immune to the disease.
Saudi spares pigeons
12/09/07
Saudi Arabian authorities have ruled out a cull of pigeons in Mecca and Medina despite the outbreak of avian flu in parts of the kingdom, reported Gulf News.
A total of nearly 4m birds have so far been killed to stop the spread of the deadly H5N1 virus but Dr Mohammad Bin Abdullah Al Sheeha, an Undersecretary at the Ministry of Agriculture, said pigeons have immunity against the disease.
While this certainly sounds like a definitive answer, anecdotal evidence for pigeons being vectors of the virus come from reports such as :
- In February of 2006, a 14 year old pigeon handler in Iraq reportedly died of the H5N1 virus
- West Jakarta, a 39 year old man died in May of 2006, after reportedly cleaning pigeon feces from blocked roof gutters at his home.
- And in this report from April 2006, a cat was infected after eating an H5N1 infected pigeon.
There are, luckily, more scientific studies available, although the results are a bit mixed.
In May of 2007, in the CDC's EID Journal, a dispatch appeared entitled Avian Influenza (H5N1) Virus in Waterfowl and Chickens, Central China, where scientists deliberately infected a variety of birds to determine their susceptibility to the H5N1 virus.
Their study suggested that pigeons may be asymptomatic carriers of the avian flu virus.
And the latest study, published in October of 2007, entitled Role of Terrestrial Wild Birds in Ecology of Influenza A Virus (H5N1) gives us this perspective.
Abstract
House sparrows, European starlings, and Carneux pigeons were inoculated with 4 influenza A (H5N1) viruses isolated from different avian species. We monitored viral replication, death after infection, and transmission to uninfected contact birds of the same species. Sparrows were susceptible to severe infection; 66%–100% of birds died within 4–7 days. High levels of virus were detected from oropharyngeal and cloacal swabs and in organs of deceased sparrows. Inoculation of starlings caused no deaths, despite high levels of virus shedding evident in oropharyngeal swabs. Least susceptible were pigeons, which had no deaths and very low levels of virus in oropharyngeal and cloacal swabs.
<snip>
Because pigeons shed only low amounts of virus upon infection and they did not transmit to contact birds, their role in the ecology of influenza (H5N1) virus may be minor.
So to review:
While bird fanciers no doubt wish that pigeons were immune from the virus, and city planners undoubtedly pray that it is so, the evidence casts doubt on that assumption.
Stating that pigeons have immunity to the H5N1 virus appears a tad optimistic, although early research indicates they are not as strongly affected by the virus as other bird species.
In Indonesia, as in China, we've seen some `immaculate infections', where no direct contact with sick poultry has been documented. Who knows how these people contracted the virus? Pigeon droppings are certainly one possibility.
The fact that pigeons seem to tolerate the virus does make one wonder if they aren't a silent reservoir of the virus, and that they may explain how the virus gets reintroduced back into an area after all infected poultry have been culled.
Obviously more research is needed.
The good news is, we haven't seen more than a few pigeon related infections, a pretty good indication that the pigeon, up till now, isn't a major threat.
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