For the Birds Radio Program: West Nile Virus
When I was a little girl, people were terrified of polio. We had a polluted creek running through our blue collar suburb of Chicago, and we children were absolutely forbidden to swim in it because the grownups were so scared of polio.
In 1952, Jonas Salk first tested on humans a polio vaccine that he developed with killed virus. In 1957, Albert Sabin did his first human experiments with the oral vaccine he developed, which used live polio virus. Before their breakthroughs, tens of thousands of people were being infected with polio annually. Many of them died, and many more became crippled. Thanks to Salk and Sabin, polio went from being a huge scourge to being virtually eradicated.
Vaccinations prevent diseases, but they don’t cure them. There are many diseases that do not have vaccines available, and some of these still don’t have cures. One of the scary ones right now is West Nile virus. This serious, potentially fatal disease was first described in Uganda in 1937. It spread to Egypt and France in the ‘60s. But it wasn’t until 1999 that the disease spread to the United States. That year there were 62 human cases in the New York City area, and 7 human deaths. There were many, many more cases in birds. Hundreds of dead crows, jays, and other birds have been found infected with the disease, beginning that year. Once the disease had a toe-hold in the U.S., it spread quickly. This year it has even been found in Milwaukee, Wisconsin.
West Nile virus is transmitted through the bite of a mosquito that carries the virus inside after biting an infected person or animal. It probably first reached the U.S. on ships from Africa or Eurasia that carried uncovered tires filled with rainwater and mosquito larvae. Now that the disease is here, it is spreading quickly. Many animals are vulnerable, including skunks, horses, dogs, cats, birds, and humans. Birds are exceptionally quick to die from it. Individuals from over 70 species have been found dead that were analyzed and found positive for the virus. But crows are obviously the most conspicuous, so the most easily found. There is no evidence at all that the virus can be spread by handling a live or dead infected bird. You only get the disease from mosquito bites.
But mosquitoes can only transmit the disease after they’ve bit an infected animal, so birds and horses and the many other creatures that get the disease do indirectly aid in the spread of the disease, as humans do, though the disease is much more fatal to birds than to humans.
We will eventually develop an effective vaccination for the West Nile virus that will protect us and our pets and farm animals. But there’s no way to protect wild birds. Ultimately, we may be facing the kind of avian extinctions on our big continent that the small islands of Hawaii suffered after mosquitoes were introduced there in the 1600s.
If you find a dead bird and no clear cause of death is observable, report it to your state department of health. No one expected the disease to appear in the Midwest so quickly, so Minnesota and Wisconsin may not be quite geared up to analyze bird carcasses yet, but need as much information as possible to study the spread of this disease, which has such horrible ecological, as well as epidemiological, implications.