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July 24, 2005

Birds As Carriers: From Avian Flu to Toxic Poop

We took a short vacation to Hong Kong a ways back. We spent Shane's birthday in and around our lovely room in a Kowloon hotel. A few weeks later, SARS hit the news, with 7 cases at a Kowloon hotel. Shane had been suffering from a post-vacation cold and for a bit we were concerned, but then we were at a different hotel, and about a month too early to be in the right time frame anyway. Still, we were relieved to find he was just suffering from the common cold (quite normal for March). Still, we listened as the media and community made a lot of gloomy predictions of pandemics and such, none of which materialized.

When I started hearing about bird flu, I gave it about as much consideration as I did a case of SARS... Because I no longer commute, I don't get to listen to NPR and the BBC news on the radio as much, so when the topic came up on a family vacation, I decided I had better read up a bit on whether I was giving bird flu its proper consideration.

What's a pandemic?

Well, let's look at the great influenza pandemic of 1918-1919. Here is another case of when a completely new influenza virus subtype emerged and spread around the globe. It was:

• The most devastating epidemic in recorded world history
• Killed between 20-40 million people in a one year period
• Considered a global disaster
• Killed more people than in the 4 years of the Black Death Bubonic Plague
• Killed more people than World War I
• Dropped the average life span in the US alone by 10 years
• Mutated, causing new waves for two more years, killing an estimated 40–50 million persons

Why Bird Flu?

Bird flu is more technically known as avian influenza. It is a highly contagious virus that occurs mostly in fowl - especially the kinds we like to eat (chickens, ducks, turkeys), but also in many other kinds of birds. Avian influenza was first discovered in 1878 in Italy. The disease was then known as “Fowl Plague”. According to the CDC, at least three of the great flu pandemics of the 20th century were the result of bird flu viruses becoming incorporated into human flu viruses, which led to a far more dangerous virus, which had worldwide repercussions.

There are currently two forms of the bird flu virus - a highly contagious one and a mildly contagious one. Over time the virus has mutated and formed for than 20 different strains, leading to considerable concern that the virus, while tolerated by most birds as a particularly bad cold, could be devastating if a highly contagious strain mutated into a human-catchable form.

A virus jumping from an animal strain to a human strain was once considered an alarmist's notion. Now it seems that most of the worst viruses of the past two decades have been the ones that have developed human-catchable forms that humans have no built-up immunity to.

Viruses are masters of interspecies navigation. Mutating rapidly and often grabbing the genetic material of other viruses, they can jump from animals to humans with a quick flick of their DNA. Sometimes, as in West Nile fever, the transfer occurs through an intermediate host such as a mosquito. But viruses can also make the leap directly.

Since the 1980s, the list of diseases that have hitchhiked directly from animals to people has grown rapidly — hantavirus, SARS, monkeypox and, most recently, avian influenza, commonly called bird flu. With the exception of HIV/AIDS, perhaps none of these illnesses has more potential to create widespread harm than bird flu does.

More at: Mayo Clinic: Bird flu

So is this a serious threat or a lot of doomsday prophesizing? Well, the "Fowl Plague" has reared its head numerous times in the past century, most recently in Asia. These outbreaks have been largely caused by a highly contagious and virulent strain, known as H5N1.

The H5N1 virus, a subtype of the avian influenza virus, is found in poultry. Scientists at first believed it was impossible for birds to directly infect humans with the virus. But an outbreak in Hong Kong in 1997 that killed 6 of 18 people infected with the virus proved the contrary.

Since then outbreaks have forced the slaughter of millions of chickens, ducks, and other birds across Asia. This year there have been 44 confirmed human cases of H5N1 flu in Thailand and Vietnam. Of these, 32 people died. There is not yet a vaccine for the disease.

Meanwhile the virus has undergone huge genetic changes and become even more pathogenic. It now affects not only birds, but also cats, pigs, and even tigers.

Experts fear the disease will mutate into a form that can leap between humans and sweep populations with no immunity. The adaptation could occur through a few genetic changes or what is known as "re-assortment" of the genes of the avian strain and the human strain. Domestic ducks and pigs are seen as likely transmitters.

More at: National Geographic: Is Asian Bird Flu the Next Pandemic?

But for the moment H5N1 is only slightly infectious to humans. Also, it cannot be transmitted between humans - only by direct contact with an infected animal. The virus is killed by heat, among other things, so proper cooking works as well as hygienic handling. For now, you really need to be handling raw guts or feces, so most commercial meat products aren't a huge concern. Many of the human cases have been poultry farm workers and others who came in contact with contaminated market stalls, etc.

According to the CDC, bird flu is spread through the birds' saliva, nasal secretions, and feces. Other birds become infected when they have contact with contaminated excretions or surfaces that are contaminated with excretions. Scientists think that the few human infections to date have resulted from contact with infected poultry or contaminated surfaces. These human cases have all been in Asia.

Health agencies like the CDC and the U.N. World Health Organization (WHO) focus mostly on preventing the spread of disease in domestic farming - especially poultry farming of ducks, turkeys, chickens and geese.

The importation of the disease is also a serious consideration, and the United States has also imposed an Embargo of Birds from Specified Southeast Asian Countries in order to keep infected birds out. This is certainly a good idea, but as we know, the black market trade on exotic animals is considerable at several billion dollars a year.

Wild birds and migratory spread of infection seem to be given less consideration in the numerous headlines regarding the bird flu. Perhaps this is because it's such a terrifying possibility with no good solution under our control. There's no way we can monitor every bird flying in and out of the country.

Migratory birds, including wild waterfowl, sea birds, and shore birds, can carry the virus for long distances and have, in the past, been implicated in the international spread of highly pathogenic avian influenza. Migratory waterfowl – most notably wild ducks – are the natural reservoir of bird flu viruses, and these birds are also the most resistant to infection. They can carry the virus over great distances, and excrete it in their droppings, yet develop only mild and short-lived illness.

More at: World Health Organization: Avian Influenza

Birds As Carriers - Not Just The Flu

People used to use birds like falcons and pigeons for correspondence, and perhaps this is just another message. Birds aren't just carrying the flu, either. They carry all sorts of other nasty things as well, including pollutants. It's no longer just about making sure to cut up the plastic rings from your soda cans and making sure you throw away your plastic bags so that these items don't end up in the water, choking poor gulls and baby seals.

Now birds are eating and walking in polluted areas and then migrating to some of the most pristine wilderness areas left in the world and depositing the pollutants there. Areas like the Arctic are showing increasing levels of pollutants not just from the currents, but also from the migratory species - especially birds.

The birds, it seems, are eating carrion, squid, and other marine animals from persistent organic pollutant contaminated seas. The flyers then return to their coastal home and deposit their contaminated prey—in the form of excrement—in local ponds, which see their persistent organic pollutant levels skyrocket as a result.

More at: National Geographic: Seabirds Fly Pollutants to Arctic Coast, Study Says

Now I look at the shorebirds flying around the county landfill and I think about what they're eating and where they're going. I see the ducks that stop at the playground pond, which has always been beyond filthy, and the little toddlers chasing the birds around on the grass. I wonder where the ducks have come from, and I feel uneasy.

This is one of those topics that makes you feel completely helpless. Millions and millions of birds are being culled at the first sign of some avian flu - often in Southeastern Asia where, frankly, they could really use the meat and the money in trade. I think of how someone with WHO or whomever would try to explain to some poor starving family why so much food is being thrown out and not eaten, "wasted". At the same time, I feel less for the birds than I feel I should - like the fear of a pandemic has distanced me from nature. I don't know which part is worse.

And it's not like we can control where every bird lands and keep them out of the pollution or the garbage. Sure, we can pay more attention to closing lids and covering refuse, but somehow all these little tasks seem rather futile, and almost laughable sometimes. But don't worry, I'll still keep doing them anyway.

Then I think of the poop, and I am really frightened. The World Health Organization (WHO) has stated that with the highly pathogenic form of avian influenza, a single gram of contaminated manure can contain enough virus to infect 1 million birds.

I live on the seashore, just as over 4 billion others do - that's more than 2/3 of the world population.

Posted by sorsha at July 24, 2005 7:06 PM