Understanding the West Nile Virus

Oct 02, 2012

Last month, the Centers for Disease Control and Prevention reported that this year's West Nile epidemic is on track to be the deadliest since the mosquito-borne disease hit America's shores in 1999. Reporter Brian Vastag contracted the virus in July and has been battling the symptoms of West Nile fever ever since. According to his article in today's Health and Science section, climate change is partly responsible for spreading West Nile to 48 states. Questions from the public still abound, with prevention as a top priority.

Vastag was online to discuss the virus, infection rate and death toll on Tuesday, Oct. 2nd.

Thanks for tuning in to this chat about my experiences with West Nile virus. Fire away!

How physically and mentally devastating is it to exist with the West Nile virus? What are some of the limitations one faces and how long do different symptoms generally last?

The course of the disease varies tremendously, from no symptoms to temporary or permanent paralysis to death. For me, I was fatigued and limited in my activities (no biking or hiking, for instance) and have been working part-time for most of the past three months. 

Hello, Mr. Vastag, I'm one of those people mosquitoes seem to flock to and several times this summer in DC, I got over a dozen bites a day. One of those times, I developed a mild fever, headache, aches and tiredness for a few days, but I've no way to know if that was W. Nile virus-related. Does it matter? If it was WNV, do I now have anti-bodies that make me resistant?

It could have been West Nile virus, as symptoms range from nothing to a mild fever to paralysis to death (in older and immunocompromised patients). If you want to know, you can ask a doctor for a blood test. Get the test for IgM antibodies - they can stay in your blood for months. There's pretty good evidence that once you have West Nile antibodies, you will have immunity for a while, possibly for life, although no one's certain. 

Are there things that can be done early to prevent West Nile from getting worse and turning into the "neuroinvasive" kind like Jeff Shane describes in the other story in the Post today?

Once a person has West Nile, it seems to be a bit of a crapshoot regarding who progresses and who does not. Older people and those with compromised immune systems are at highest risk for neuroinvasive WNV. The neuroinvasive symptoms usually appear early, with the initial fever. Bad headaches and headaches are some of the symptoms. This variety of West Nile illness can be quite serious. So, to answer your Q, I have not read or heard of  anything a person can overtly do to prevent West Nile from going neuroinvasive. It either does or it doesn't. 

So how many times did you get tested and why didn't it show up right away? Second question, what is the CDC doing about this, if anything?

I got first got a blood test during the first week of my illness. But it can take up to 8 days for high levels of blood antibodies to appear, so my first test came back negative. Only six weeks later when another doctor ordered another test did it come back positive. As for the CDC, they track WNV and push out prevention messages - wear bug spray, cover up outside, get rid of standing water where mosquitoes breed. 

Have you been able to find the right experts who can diagnose this and treat you?

Thanks for asking. It took a long time to get a diagnosis. My first doctor didn't recognize it. Eventually, an infectious diseases specialist diagnosed it after a positive blood test for WNV antibodies. As for treatment - there is no treatment. Drug companies stopped development of drugs for WNV. There isn't a lot of money in it for them - there are just a few thousand reported cases each year, not enough to invest the huge money it takes to bring a drug to market. 

It seems like doctors around here don't recognize that West Nile is an issue now. Should we all be using bug spray from April-December?

My experience with a primary care physician who did not recognize it suggests there may be an issue with doctors in this area not being aware of it. And yes, bug spray while the mosquitoes are out is a great idea. You never know which one of those guys is going to be carrying the virus. That said, most people bitten by an infected mosquito (maybe 60-80%) never get ill. No one knows why some people get sick and some don't. 

Brian, I'm so sorry to hear this news, as you know the nonprofit EcoHealth Alliance is on the front lines of predicting and preventing the next possible pandemic. My question is simple...do you think the general public understands that over the past 50 years that at least 75 percent of the disease outbreaks we are dealing with are wildlife-born and then transmitted to people? And it's not the fault of wildlife but the human-induced changes in the environment that are causing that threatens public health.

Thanks for the Q. Well, I've never seen a poll of awareness of zoonotic (animal to human) diseases, so I don't know. I'd guess most people are not aware that many or most human illnesses - especially the emerging diseases like West Nile - are caused by animals. A great book on this subject just came out. It's called Spillover by David Quammen. I started it last night and it's gripping. 

Someone else must have a question...don't be shy. 

So is climate change the reason this is going to be what the CDC says is the worst year ever for west nile? Or is it just that people are reporting it more now that we know about it?

If you read my piece in today's Post, you can find a summary of the evidence that climate change has made this year a particularly bad year for West Nile. The extremely unusual weather this year - which has the fingerprints of human-induced climate change all over the place - has provided ideal conditions for WNV to thrive this year. http://www.washingtonpost.com/national/health-science/a-science-reporter-becomes-a-west-nile-zombie/2012/10/01/6bab8c2a-091d-11e2-afff-d6c7f20a83bf_story.html  

I know West Nile supposedly came to New York in 1999 but how did it get there?

As near as anyone can tell, a stowaway moquito hopped on a transcontinental flight. There is no direct evidence for this - that is, no one found the culprit (it would be pretty much impossible to trace a mosquito anyway) but that's the best answer anyone has come up with. It is informed speculation, however. It's important to note there is no human-to-human transmission of West Nile. People can only get it from infected mosquitoes. 

How did you know to go to an "infectious-disease specialist"? When was your breaking point?

Well, my first doctor kind of gave up trying to figure out what was wrong. A few friends, including my colleague Lena Sun, who has reported on WNV, told me my symptoms sounded like West Nile illness. Eventually that message got into my thick skull and I decided to see an infectious diseases doc, who tested me for everything that can be tested for. I'm thankful I go to him, as I was starting to worry I had something really grave like leukemia.  

Brian, I'm glad you are reading Spillover, I just started reading David's book too. I think it is important for people to understand that conservation is just more than protecting exotic animals, and creating safe habitats. Climate change, global trade and travel as well as deforestation among other environmental impacts are making us and our families sick. How can we as communicators effectively get this message out so people can really understand that these diseases are not going away and in fact we will see more and more outbreaks.

Those are really good points, thanks for making them. I think personal stories can be effective - showing people the connections that have spread these emerging diseases. The world is connected now, and that means there are viruses that once were contained can now travel the globe. But I think it's hard for everyday people to know what to do about it. If a forest gets clear cut in Niger, how can that possibly affect me here in Washington? It's a tough connection to try to make for people. My favorite line in Spillover is this: "You shake a tree, things fall out." We're shaking a lot of trees all over the world, and a lot of diseases are falling out.  

If climate change and globalization are to blame for West Nile's migration to the states, why hasn't the same happened for other mosquito-borne illnesses like malaria? Why didn't we have a "worst year ever" for malaria?

That's a great question. There are  a lot of factors at play here. Some of it is happenstance. A moquito carrying WNV arrived in NYC in 1999, where it found ideal conditions. It was a very hot summer there, which amplifies the virus and helps it spread. But if that mosquito had been carrying malaria, or Rift Valley fever virus, or something else, would that disease have gotten a foothold? It's hard to say - and we sure don't want to run those experiments. Dengue fever is now in the Florida Keys and South Texas. Experts at CDC and elsewhere are on high alert for the next tropical disease. They're worried about Rift Valley fever, especially, which resembles West Nile and can infecte livestock + people. 

Brian, do you have a sense of the number of people in the U.S. infected by the virus this year? (I'm assuming it's hard to get exact numbers since some may go undiagnosed)

The CDC has gotten reports (from state health departments) of about 3,500 cases of West Nile illness so far this year. But that's a gross underestimate. Kyle Petersen, head of West Nile research at CDC, published an estimate of 400,000 to 1 million West Nile illnesses in the US since 1999. That estimate comes from sampling  various populations and checking their blood for WNV antibodies. Many people may be briefly ill with a fever, never see a doc, and have no idea they had West Nile. The good thing is, they are probably immune from ever getting it again.  

In a nutshell (if that's possible), how do viruses such as Ebola become contagious between humans? Or do they start out that way? And--if horses can get WNV, will other mammals such as dogs and cats?

That's a very good question. Thankfully, West Nile virus can not be transmitted between people. And H5N1 flu, or avian influenza, looks like it rarely if ever gets transmitted between people. That's good. But viruses, as they replicate in a human cell, can accumulate mutations. Some of those mutations may make the virus better at jupming between people. That's why the CDC and WHO have put such huge effort into surveillance for H5N1 and other potential killers. They want to know the minute it begins jumping between people and then they will rush in to try to stem transmission. 

What's the long-term prognosis for people who have had West Nile? Does it ever really go away, or will you be dealing with the consequences for the rest of your life? (Sorry.)

No problem. There is some research suggesting that some proportion of people who get WNV and have a fever from it end up with long-term problems like fatigue, memory problems, and so on. There are support groups for survivors. Some patients take Provigil, a medicine for narcolepsy, to try to get more energy. But the truth is there just has not been a lot of research on WNV survivors. Here's one study suggesting long-term issues with a group of patients: http://cid.oxfordjournals.org/content/43/6/723.full

If private drug companies aren't working on a vaccine or treatment for WNV, is the government (CDC etc) doing anything to develope a vaccine? It's unfathomable that nobody is working on a vaccine for this serious, debilitating disease!

The are 4 vaccines used to protect horses - but they have not been put through the very expensive FDA approval process for use in people. A vaccine for people might not really be a great idea anyway - it's unclear what the vaccination strategy would be. You would not give the vaccine to the entire country to prevent sporadic outbreaks. And it's impossible to predict where WNV might pop up from eyar to year. So a human vaccine probably doesn't make sense anyway. A drug for treatment though - that would be a great idea. But there are no clinical trials of WNV drugs ongoing in the US. 

Brian! I hope you get better. I haven't read the story yet, but do you know exactly when and where the bite happened that gave you WNV? Do you think the experience has the potential of turning you into an advocate rather than a reporter?

Thanks much. I don't recall a specific mosquito bite, but it likely happened the week of the Fourth of July. (Happy birthday, America!) I don't really notice mosquito bites because I grew up in Wisconsin and Minnesota spending the summers getting eaten up by skeeters. Around here, they seem not very prevalent by comparison. 

Is there any indication that the increase in WNV seen this year is related to severe declines in bats as a result of White Nose Syndrome, a recently emerged disease of bats? These bats are presumably natural predators of the mosquitoes that spread WNV.

That's a very interesting question. I don't know if anyone has looked into it. But I'm all in favor of more bats eating more mosquitoes. I hope some ecologists look into this connection. Bats are our friends!

You mention that the frequency of WNV replicates faster under warmer conditions. Is there data on how the carrier frequency in the mosquito population changes under warmer conditions? Also, what is known about how the vector titer in the mosquito relates to the likelihood of a person getting infected, or to the symptoms they express?

Here is some stuff copy-and-pasted from my story notes that might help answer that: 

Lab study, 2008, PLoS Pathogens

“In addition, we found that transmission of both strains of WNV accelerated sharply with increasing temperature, such that small increases in temperature had relatively large effects on transmission.”

 http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1000092

 2001 lab study – mosquitoes pick up, grow virus better in the heat:

 http://www.bioone.org/doi/abs/10.1603/0022-2585-39.1.221

 In mosquitoes held at 30°C, virus was recovered from nearly all mosquitoes tested, disseminated infections were detected as early as 4 d after the infectious blood meal, and >90% of all mosquitoes had a disseminated infection 12 or more days after the infectious blood meal. In contrast, for mosquitoes held at 18°C, disseminated infections were not detected until 25 d after the infectious blood meal, and even after 28 d, <30% contained a disseminated infection. Results for mosquitoes held at 20 and 26°C were intermediate for both infection and dissemination rates.

 2008 lab study

http://online.liebertpub.com/doi/abs/10.1089/vbz.2007.0101?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%3Dpubmed

 Mosquitoes fed blood meals containing 6.2 logs plaque-forming units (pfu) WNV/mL and held at 25°C, 28°C, or 30°C for 13 days exhibited significantly different rates of infection (30%, 52%, 93%) and dissemination (33%, 22%, 81%) across temperatures.

So glad you are on the road to recovery. Do you think there will be more research to develop a prophylaxis like there is for malaria?

Thank you, much appreciated. Malaria is a parasite with a complicated life cycle that presents opportunities for drug prophylaxis. West Nile is a virus and so the only defense is in your immune system. A vaccine could boost immunity and provide protection, but as I said earlier, there are no vaccines in development for human use. 

Does WNV linger in your nervous system to keep you so ill for months? Will it ever be killed off (i.e., does your doctor think you'll eventually be ok)? Sad about pharma's not wanting to invest research dollars in a cure.

Thanks. There has not been a lot of research into long-term effects of WNV, so there are a lot of unknowns. There does seem to be a group of patients who feel symptoms for years. An expert in Mississippi who has treated many patients, Art Leis, told me he thinks the virus is expelled from the body fairly quickly, but the immune system gets so wound up it keeps chugging along, in an almost auto-immune-type reaction. He thinks that's where the long-term symptoms come from. But it's just a hypothesis at this point - a lot more research is needed. 

How are you feeling now?

Thanks for asking. Still feeling a lot of malaise and kind of feverish (despite having a normal body temperature). It's a difficult sensation to describe. Kind of a hollow feeling in my head and after a few hours of normal activity I get pretty tired. It's frustrating. 

Hi Brian, you may not have the answer to this question. But how much does it cost to make and distribute a vaccine for an illness like West Nile? If it's less than the 200 million in direct costs for the virus epidemic in 2002, then maybe we should concentrate on a vaccine. What do you think?

I don't think a vaccine makes sense for WNV. You wouldn't want to vaccinate the entire country for it and it's impossible to know where it's going to pop up from year to year. I think more money should be invested in drug treatment. One researcher told me that drugs in development for dengue fever virus might also work against West Nile, which is a pretty similar virus. So that's a spot of good news, as there are several dengue drugs in development. Globally, dengue is a much bigger problem than WNV. 

Also, I want to add something about how undereported this disease is. I am the third person with confirmed WNV in DC this year - but it took more than 2 months from onset of my fever until my case was confirmed. So the reported case are just the tip of the iceberg. 

Any more Q's? 

A flock of crows (they harbor WNV and infect mosquitoes) just flapped by my window. I think that's a sign to wrap things up. Thank you for all the great questions. 

Have they been tracking crows, I heard they are carriers of the disease and can infect mosquitos?

Early on, researchers did track dead crows and other carriers. But that doesn't make much sense to do know, Laura Kramer of NY State Dept of Health told me, because most birds now have some immunity to WNV so they don't drop dead from it. And it doesn't make sense to do random samples of crows. We know WNV is here in the US, and it's here to stay. 

Bats are great, but there is no predator that eats enough mosquitos to make a dent in the population. It isn't the main food for anything.

Thanks for that. 

Thanks for all the great questions. I'm going to wrap it up now. Remember: Wear bug spray, get rid of pools of dirty water, and shoot a few crows for me. 

In This Chat
Brian Vastag
Brian Vastag is a science reporter at The Washington Post, where he covers general science, the environment, climate change, health and space. From 2004 to 2010, Vastag freelanced for over 40 publications, including U.S. News & World Report, New Scientist, Health, Nature, Science, Scientific American, Science News and National Geographic News. From 2000 to 2004, Vastag served as Washington news editor for the Journal of the American Medical Association. Vastag has made live radio appearances on BBC World Service, WNYC, and Public Radio International's The World, and television appearances on MSNBC and CNN Headline News.
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