West Nile Virus Depends on Robin Distribution

A recent study of West Nile Virus transmission in the DC area found that the number of infections in humans depends on the density of the local population of American Robins. Researchers set up mosquito traps baited with dry ice in several local parks: the 26th Street Dog Run, National Mall, and Fort Dupont Park in DC; and Camden Yards, Takoma Park, and Bethesda in Maryland. Birds at the same sites were caught in mist nets for blood tests.

Robins, it turns out, appear to be taking the hit forhumans, getting sick and dying as did thousands of crows that wereinfected in the first wave of West Nile virus after it arrived in NorthAmerica. Thanks to the robins, humans who frequent the 26th Street dogpark and similar areas have a lower chance of contracting the virus, atleast in spring and early summer months. The reason? To mosquitoes,robins are far more tempting meals.

Then the scene changes.

"Robinsbegin to migrate south in late July and August," Kilpatrick said,"leaving mosquitoes on the hunt for blood from another source."

That source turns out to be Homo sapiens. The number of human infections with the virus shoots up come the dogdays of August. Then it's mosquito vs. man or woman, instead ofmosquito vs. robin.

The authors of the original article in PLoS Biology argue that the pattern of infection - birds in early summer and humans in late summer - has increased the prevalence of the disease in both mosquitos and humans:

Feeding shifts have two synergistic effects on the intensity of WNV transmission to humans. First, we have shown that the increase over time in the probability of Cx. pipiens feeding on humans results in a greater number of human WNV infections than if the mosquitoes fed on humans with the same probability as in early summer (Figure 1C). Second, feeding primarily on WNV-competent avian hosts during the amplification period of the epidemiological cycle maximizes the intensity of the epidemic in mosquitoes.... This is because mosquito WNV prevalences are already beginning to decline (possibly as a result of increased acquired immunity in juvenile birds) when mammals begin to make up an important fraction of the blood meals. Thus, the shift in feeding from competent hosts early in the season to humans later leads first to greater amplification of the virus as transmission intensifies between birds and mosquitoes and subsequently to an even greater number of human WNV infections.

The continuing presence of the West Nile Virus in the DC area is a reminder to take reasonable precautions against mosquito bites, especially in late summer: do not keep standing water around your house; use insect repellent on bare skin or keep skin covered. (See this CDC advice on avoiding bites.)

Doctor and Birdwatcher On Call For Bird Flu

Metehan Özen, middle, sets up bird-watching gear with friends at Turkey's Karakaya lake.

Excerpted from THE WALL STREET JOURNAL article by PHILIP SHISHKIN

On a recent Sunday, Metehan Özen -- one of Turkey's foremost birdwatchers -- trained his $1,500 Leica telescope on an orange-chested Merlin falcon and watched it devour a smaller bird in a flurry of claws, flying feathers and blood.

A few days earlier, two boys played with a dead crow, developed a fever and were brought to Dr. Özen's pediatric hospital ward. There, the specialist in infectious diseases monitored them closely for signs of bird flu.

For years Dr. Özen's hospital job and his hobby existed in unconnected worlds. As Turkey grapples with the bird-flu outbreak here that has quickly infected at least 21 people and killed four, the doctor's two callings have put him in the middle of the quest to understand the virus and contain its spread.

Fellow doctors used to tease him about birdwatching. Not anymore. Over the past two weeks, as the virus rolled out across Turkey, the 37-year-old Dr. Özen briefed the country's top public-health officials about the epidemiology of avian flu and about the migratory routes of wild birds. They are suspected of introducing the virus to domestic poultry, which in turn can infect people. He took a long bus drive amid heavy snowfall and howling wolves to get to the scene of the first human cases near the Southeastern town of Van. There, he saw infected children and their chest X-rays, and visited the parents of three who had died. He helped draft the government's measures to combat the virus, including culling poultry and isolating domestic birds from humans and wild birds, and persuaded officials to ban the hunting of all wild fowl.

In September, Dr. Özen warned colleagues at a medical congress that wild birds could bring avian flu to Turkey during the winter migratory season, and that is now an accepted theory. Trade in infected poultry is another means for the virus to spread. "When you compare maps of migration patterns with maps showing bird-flu outbreaks, they often match each other," said Mehmet Ali Torunoglu, the head of the communicable diseases section at Turkey's ministry of health. "Metehan seems to be right."

In late 2004, Dr. Özen tracked a satellite-tagged goose as it flew from Northern Russia, down to Kazakhstan, Eastern Turkey and Iraq, and then back. The goose's stops along the route gave Dr. Özen ideas about how the virus could spread through migratory flyways.

After visiting Van, Dr. Özen spent some time working with a team of experts at the Turkish health ministry's crisis center in the capital of Ankara. When he returned home, bad news awaited him at his hospital. The two young boys who had found a dead crow in their backyard had a mild form of viral pneumonia, a possible symptom of bird flu. In its human form, the virus often attacks the lungs and causes them to fail. Dr. Özen put the boys in an isolated ward, and waited uneasily for the results of tests that can determine bird flu.

They came back negative. So after his tense week, Dr. Özen headed out into the countryside for his usual pastime, but with a difference: Avian flu was never off his mind. Now, "every bird you see is suspect," Dr. Özen says.

He awoke at 6 on Sunday morning and set off to explore the rich avian world of the Karakaya lake on the outskirts of Malatya, an Eastern Anatolian town known mostly for its apricot orchards. Accompanied by two buddies -- a plastic surgeon and a railroad worker -- Dr. Özen was soon announcing the sightings of particularly interesting birds by chanting "aha, aha, aha...ha-ha-ha!"

A stocky beige barn owl, drowsy and slow in the early morning sunshine, was being chased and harassed by two nimble magpies swerving around it like two fighter-jets. A group of gray herons, their long necks recoiled for a nap, stood motionless on the shore. Two pygmy cormorants, an endangered species, flew across the bright blue sky. Thousands of ducks and Armenian gulls, their numbers swelled by winter migration, crisscrossed the lake.

In the village of Toygar, right on the shore of the Karakaya lake, several roosters crossed the road and headed toward the water to mingle with hundreds of wild ducks. "This is exactly what I fear," Dr. Özen said. For most people, close contact with wildfowl is extremely rare, but domestic poultry routinely mix both with wild birds and with people. Sure enough, two children hopped off a donkey cart next to a wooden shack and approached the roosters.

Since then, he has sighted around 370 species out of Turkey's estimated 456, and he is at work on a "Birds of Turkey" volume. He and his buddies are now preparing a trip to look for a bird called the Great Bustard because at 26 pounds it's the heaviest thing flying in these parts.

Bird Flu Puts Ravens At Risk And British Empire?

One of the Tower of London's ravens is seen roosting in 1996.
Photo Credit: By Lynn Fergusson -- Reuters

For 350 years, coal-black ravens have wandered freely around the Tower of London's grassy inner courtyard as cawing barometers of the monarchy's vitality -- if the ravens ever die or leave the tower, the legend goes, the tower and the kingdom will fall.

Now the fear of bird flu has done what Luftwaffe bombings, blizzards, assassinations and abdications could not, forcing the ravens to be moved inside in isolation for their own safety and to hedge Britain's bets on the future of the crown.

On Tuesday, Hungarian officials confirmed that they had found the lethal H5N1 strain in three dead swans. With seven European countries now reporting cases of bird flu, including France, which is just 21 miles across the English Channel, concern is spreading in Britain. European officials met Tuesday in Brussels to discuss how to contain the virus, which has killed at least 92 people, mostly in Asia.

The British government has announced that plans are being prepared to put millions of free-range chickens indoors if the disease reaches British shores. But, quietly, the country's most famous birds were moved indoors last Wednesday night to custom-made aviaries. The names of the eight ravens currently in the tower are Gwylum, Thor, Hugine, Munin, Branwen, Bran, Gundulf, and Baldrick.

The move was made public this week by Her Majesty's Royal Palace and Fortress, as the tower is officially known, as visitors continue to inquire as to the whereabouts of one of the favorite features of the 900-year-old tower.

As thousands of visitors arrived Tuesday to view the famed Crown Jewels, several discussed the ravens that were seen no more. No one was saying nevermore would they be seen, but officials said the quarantine is not likely to be brief.

* Read more from The Washington Post
* More on Ravens and Tower of London the from Wikipedia

Flu Facts

Bogdan Cristel

With widespread interest in avian influenza or “bird flu”, Audubon is providing the following information and links as a resource for those who may be concerned about avian influenza, as well as about how birds are involved. Also included are some general precautions for protecting both human and bird health.

Background on Avian Flu
There are over 135 different strains of avian influenza virus. Most strains circulate in low levels within wild bird populations. Though they usually cause only mild illness in wild birds, some strains may cause lethal outbreaks in domestic poultry. A few avian influenza strains are more virulent, and can cause high mortality in both wild birds and poultry stocks.

Most avian influenza strains do not normally infect species other than birds, though a few subtypes can be transmitted from birds to humans. Avian influenza viruses become much more dangerous if they mutate to allow easy transmission from one human to another, not just from birds to humans. The most devastating avian influenza epidemic occurred in 1918 when a highly pathogenic strain of avian influenza mutated allowing people to infect other people. An estimated 40 to 50 million people died worldwide as a result.

The Current Strain of Avian Influenza: H5N1
Since 1997, the H5N1 strain of highly pathogenic avian influenza (HPAI) has infected over 100 people and caused at least 65 deaths in East and Southeast Asia. While any human infection is cause for concern and action, this current avian flu outbreak has affected a relatively small number of people, and has very limited ability to be transmitted from person to person. Rather, the virus appears to be transmitted to humans through consumption of or direct contact with infected poultry or contaminated surfaces. Over one million domestic birds have been culled to contain outbreaks. There is no evidence that the virus has mutated to spread widely from person to person.

Do Wild Birds Transmit H5N1 to People?
In the summer of 2005, the virus spread to Central Asia and China where it was detected in both domestic birds and wild birds. These outbreaks do not indicate that wild birds are effective carriers or reservoirs for the H5N1 virus. The virus is so virulent that it appears to be self-limiting; infected wild birds die before they can travel far or transmit the virus to many other birds.

Leading experts including the World Health Organization, Food and Agricultural Organization of the United Nations, and World Organization for Animal Health all emphasize that culling wild bird populations is highly unlikely to stop the spread of the disease, and would only divert resources away from more important disease control measures.

(See statements by UN Food and Agricultural Organization)

Has H5N1 Been Found in North America?
The H5N1 avian influenza virus has not been found in wild birds in North America. There is a remote chance that infected wild birds from Asia could bring the virus with them during fall migration to North America. The US Fish and Wildlife Service, US Geological Survey (USGS), Alaska Department of Fish & Game, and public health agencies are working together to test thousands of waterfowl and shorebirds for the virus in Alaska, and field sampling is being integrated with surveillance programs throughout the United States and Canada.

What You Can Do
1) While the possibility of contracting the H5N1 virus from wild birds is very unlikely, people who have close personal contact with wild birds should take measures to protect themselves by practicing animal handling and sanitary practices recommended by the USGS National Wildlife Health Center Wildlife Health Bulletin #05-03.

2) People who feed birds are not at high risk of contracting avian influenza from birds in their yards or at their feeders. However, since birds can transmit other diseases to humans (e.g. salmonellosis), people who feed birds should routinely clean their feeders and bird baths as recommended by Audubon and the USGS National Wildlife Health Center. People who come into contact with wild bird excreta should thoroughly clean up with soap and water.

Additional Resources
*Centers for Disease Control
*United Nations Food and Agricultural Organization
*USGS National Wildlife Health Center
*BirdLife International Statement on Avian Influenza
*Wetlands International Statement on Avian Influenza
*NPR Bird Flu in Depth
*Latest News from Google News