09-01-2002, 02:28 PM
Will West Nile Virus ever simply just die out? Or will it stick around for a long time? If it didn't die out would it infect many more Americans?
09-01-2002, 05:06 PM
I think we can safely conclude that West Nile virus will now be a permanent resident of North America. It certainly will infect many more Americans - but what the media hoopla is neglecting to tell people is that most people who are infected are COMPLETELY asymptomatic. Deaths from West Nile infection are actually uncommon. And it's not the only such virus in North America - St. Louis encepalitis, La Croix encephalitis, and the equine encephalitis viruses (Estern, Western, and Venezuelian) have all been around for a long time - but we don't hear the newspapers blathering about those, so most people don't know about them.
artemis makes excellent points. If you have been spending time outside in an area where it is endemic for a couple years, you probably already had it and didn't realize it.
Thus "more people" will get the virus only up to: it completely spreads throughout all susceptible areas of the US and the vast majority of of exposed people get it. After that, it will mainly hit children who hadn't been previously exposed. Since their immune systems are likely to be healthy, there will be very few fatalities down the road. Immune-depressed people will continue to be the problem.
Also, their main vector are corvids (crows, blue jays, etc.). Unfortunately it is quite fatal to them so the number of WNVs out in the wild will be quite lower eventually. (But it does infect other birds and animals, just not so effectively. It might species jump at some point.)
Keep in mind that over 1600 people die each day from the effects of tobacco products. A couple deaths a week is insignificant and going into hysterics about WNV is just plain stupid.
That's the good news. Now the bad news: There has been a report (http://story.news.yahoo.com/news?tmpl=story2&cid=585&ncid=585&e=3&u=/nm/20020901/sc_nm/health_westnile_dc) that suggests that 4 people received WNV from transplants or transfusions. 1 of whom died. That is a serious fatality rate compared to the normal rate. If true, the real danger from WNV will be from transfusions and since there is no quick test for WNV, uh-oh.
Thankfully, the US is forging full steam ahead on stem cell research so we won't have to rely on transplants/transfusions in the future.
09-01-2002, 06:27 PM
This is what I learned from my friend who is licensed to spray for mosquitos (he is a city employee). He has to go to classes each year to learn about the pests & the pesticides:
The particular mosquito which carries the West Nile Virus is called "QX" ~ that is a shortened version of its long name (sometimes it is called the southern housefly mosquito (?)). This is the only one (so far) which scientists have determined carries the WNV ~ out of about 50 species of mosquito found here in Mississippi. The mosquito lays its eggs in still water, or in places which will be submerged in still water later. It especially likes sewage (specificall, shit). If the water is running or aerated the egg will not survive.
Only 1 out of 150 people clinically diagnosed with WNV will realize that they have it. Although not specifically proven, the health department's opinion is that once you have it, you will not succumb to it again. It is likely that lots of us have already had it and just don't know it.
The QX is a night flying mosquito. It will usually fly for 2 to 3 hours following dusk.
If you are going out, wear long pants, socks & shoes, long sleeves, etc. Get rid of standing water blah blah blah. I think you know all that.
I also read this in the newspaper:
"most people infected with the virus may never even realize they are ill. A mild infection may confer lifelong immunity... In areas of Africa where the disesase is endemic, it is a mild childhood malady that almost never develops serious consequences... As the national immune system adjust, the virus may fall back into the obscurity of wildlife diesases...it will fade into the sporadic background noise of public health. ... The virus is most dangerous for children, the elderly and people with weak immune systems."
For more info see the state department of health's web site at:
09-01-2002, 11:41 PM
That's an interesting link, ftg about transplants and I'm seeing a little more about it now on the news. I feel better about not donating blood since I catch birds in WN areas to look for exposure. (I had called Red Cross about that after 9/11 and eventually they suggested that I hold off. :eek: ) Well, we're building a blocking ELISA lab so we don't have to send our WN samples out and I guess I'll just add mine to the mix and find out once and for all. If I've been exposed, I most likely only show antibodies now anyway.
NinetyWt, I think that 1 out of 150 ratio is the number of cases that will develop into a severe neurological infection. Yes, that's fairly low, but if you're one of those that end up hospitalized, the outlook is not quite a bed of roses. This is an encephalitic disease, and the long-term morbidity (http://www.annals.org/issues/v137n3/full/200208060-00009.html) is rather unpleasant "One-year follow-up of the 1999 New York patients by the New York City Department of Health found frequent persistent symptoms (fatigue, 67%; memory loss, 50%; difficulty walking, 49%; muscle weakness, 44%; and depression, 38%)." And this year, the outbreak has been considerable. Currently there are 638 cases (as compared to 48 last year), with 31 deaths. Here in New Jersey, September/October is our peak season. The season may last longer in more southerly states.
I guess the point of this is that, yes, the media has gnawed on this like a dog with a juicy bone. Most of us won't even realize we've been exposed, but for some, there can be a risk. Fortunately, as NinetyWt suggests, it's easy to avoid becoming a "dead-end host" (just refers to the inability of humans to act as a reservoir) through simple mosquito control measures. When I go out to catch birds, I wear long-sleeve turtleneck shirts, long pants and muckout boots. I'm actually more concerned about Lyme disease, so I spray with Permanone in high tick areas. I'll use a deet-product if the mosquitoes are particularly bad since I'm usually trapping in areas where positive mosquitoes have been found (and also in EEE foci areas).
Get rid of standing water, change birdbaths once a week, clear gutters. Here's a link for more that you can do (http://www-rci.rutgers.edu/~insects/ipm.htm) Also, if you have a lot of mosquitoes coming from areas off your property, call you local mosquito control agency (NinetyWt's friend). They'll come out and trap the mosquitoes to see if they are a species of concern. We have 63 species in New Jersey, and most of them do not warrant control. They might be also responsible for sending in mosquito pools for testing. They may do control. ranging from larviciding to adulticiding, and possibly some water management. And finally, if you find a dead crow or hawk, call your heath department (or check this page for state links (http://www-rci.rutgers.edu/~insects/disease.htm) to see what to do. Dead birds (and equine cases) have been the primary way for health officials to track this disease.
The primary mosquito that is found to be positive is Culex pipiens, but there are a number of mosquitoes that can be involved (see this species list (http://www-rci.rutgers.edu/~insects/poswn.htm), about two-thirds the way down). There are some species that are more competent at passing the virus. Cx. pipiens is primarily a bird-feeder (hence its dominance in the viral cycle) but will also bite vertebrates (like humans, and our dogs - it also transmits dog heartworm).
The pattern of WN is one that strongly suggests a basic arboviral cycle of infected bird-mosquito-bird and the jump last year to Florida implicates migratory birds. With Eastern Equine encephalitis, we think that the virus "recrudesces" or re-appears in birds previously infected during times of stress. This includes migration, getting a territory, getting a mate, making a nest, making kids, and raising them. With EEE, the virus comes out of hiding in whatever tissue and the bird becomes viremic, sometimes only for hours. At this time, a female mosquito is on the hunt for a bloodmeal so she can lay her eggs. She feeds off the bird and takes in virus. Amplification (and spreading) of the virus occurs when she goes back to feed off another, uninfected bird, maybe a tasty juvenile. Now this juvenile bird becomes infected, and NEXT year can play the role of re-introducing it to the mosquito population. West Nile is here to stay (not too surprising from the most widespread flavivirus). Another player in our viral background.
So, what is it with crows and West Nile? I don't know why the corvids (crows, ravens, magpies, and jays) are so sensitive, but they show this same sensitivity in the Old World too. Their populations will show some immunity (as ours are beginning to, we think - I'll find out in about a month when I start sampling crows again here), but they are still pretty sensitive to viral effects. But they are not the only birds that can act as a reservoir (see the above species list - some of those can also produce a healthy viremia needed to pass the virus on). Other viruses can have pretty devastating effects on certain birds. I saw a presentation a few years ago on EEE and emus - hemorrhagic deaths that made their pens look like an abbattoir. Yuck. But as WN becomes established in the long term, most birds probably won't see such terrible results. For example, about 70% of the Blue Jays Cyanocitta cristata in south Jersey carry the EEE virus with no ill effects. Most birds carry it at far lower population percentages. It's very likely that WN will follow the pattern that St Louis encephalitis virus, a close relative, follows: sentinel birds (House Sparrows Passer domesticus and House Finches Carpodacus mexicanus) signify an outbreak when viral levels reach something like 2.5 % in endemic areas.
Wow, WN posts release a sort of stream-of-consciousness thing from me.
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