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The Best Science Writing Online 2012
Showcasing more than fifty of the most provocative, original, and significant online essays from 2011, The Best Science Writing Online 2012 will change the way...
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The higher temperatures, humidity and rainfall associated with climate change have intensified outbreaks of West Nile virus infections across the United States in recent years, according to a study published this week.
One of the largest surveys of West Nile virus cases to date links warming weather patterns and increasing rainfall--both projected to accelerate with global warming--to outbreaks of the mosquito-borne disease across 17 states from 2001 to 2005.
The authors predict the pattern will only get worse. "If temperature and precipitation are influential in determining West Nile virus infection risk, such changes would likely increase the burden of this disease in coming decades," the authors note in the study, published online Monday in the journal Environmental Health Perspectives.
In the study, Jonathan Soverow of the Beth Israel Deaconess Medical Center in Boston and colleagues at Toronto's Hospital for Sick Children and the Harvard School of Public Health matched more than 16,000 confirmed West Nile cases in 17 states to local meteorological data.
The team found that warmer temperatures had the greatest effect on the virus' transmission to humans. Higher humidity, heavier rainstorms and increased precipitation were also tied to higher rates of West Nile virus infection, according to the study.
"A lot of the trends we see depend on local conditions," said Roger Nasci, an entomologist at the U.S. Centers for Disease Control and Prevention who studies vector-borne diseases but was not involved with the study. "West Nile virus is a very focal disease. It's not uniformly distributed across the U.S."
West Nile virus led to 43 deaths in 2008 in the United States. More than 1,300 infections were diagnosed last year, according to the CDC.
Humans can become infected if bitten by a mosquito carrying West Nile virus. Around 20 percent of infected people show symptoms of the disease, such as fever, headache and nausea. Of those, about one percent develop neurological symptoms such as numbness, convulsions and paralysis.
Warmer weather helps spread West Nile virus because it extends the length of the mosquito season, said Vicki Kramer, chief of the vector-borne disease section at the California Department of Public Health.
Higher temperatures also let mosquitoes reach biting age sooner and speed multiplication of the virus within insects, said Kramer. Thus in a warmer climate not only are there more biting mosquitoes, but those mosquitoes carry more copies of the West Nile virus, making them more likely to infect their human targets.
"It takes a while for the disease to build up," says Kramer. "That's why we see more cases in August than in June."
Rainfall's effects on mosquitoes and West Nile virus are more complicated, cautioned Bill Landesman, an ecologist at Rutgers University. For example, although their eggs need standing water to hatch, mosquito populations often flourish after a drought because mosquitoes can re-colonize faster than other insects.
"We're wrestling with this interplay of abiotic (physical) factors, mosquito populations and the West Nile virus," said Landesman, "and that sometimes makes things difficult to understand."
The new study by Soverow's team may help researchers make sense of some of these complex interactions.
For example, the study found that a single rainstorm resulting in at least two inches of rain could increase infection rates by 33 percent, while smaller storms did not. Heavy rainfall increases humidity, which can stimulate mosquitoes to bite; it also creates pools of water in which mosquitoes can breed.
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Reply | Report Abuse | Link to thisnot only mosqutio but also other insects can transmit the virus.
Reply | Report Abuse | Link to thisAAAA+ - Another Asinine Alarmist Article ; The article pre-supposes that warmer temperatures would lead to more rainfall. Meanwhile other articles in SCIAM pre-suppose that warmer temperatures lead to drought. Heads I win; tails you lose. No science here.
Reply | Report Abuse | Link to thisMy 12 year old son knows more about science than these editors.
Forgive me, but some comments are just laughable. They say a little knowledge may be dangerous. Global warming in general means warming climates over the globe. It also means droughts in some places where there was rains before, and heavy rains in some places where it was dry before. Glaciers will thaw and sea level will rise. Food sources will change and some will go extinct. Most probably new deadly disease will come out and dormant disease will surge. These are just a few. These are facts and is happening right now. I do not think this is an asinine alarmist article. All we have to do is learn more and think deeper. Do not dwell on a shallow arguments.
Reply | Report Abuse | Link to thisAAAA+ still sums it up. "Climate Change" is a meaningless term in anything other than a political arena, as it sidesteps the issue of Anthropogenic Global Warming and intimates that any change in temperature, up or down is somehow unnatural, undesirable, and created by man. And that people, if only we try hard enough, or spend enough money, that we can somehow stop the Earth from evolving. Pure poppycock...
Reply | Report Abuse | Link to thisOf course the climate changes; it is written all over the geological record. And new diseases evolve and spread through different vectors; this is written in our genes. But this article presents an unproven hypothesis (AGW) as the vector for the spread of disease without a lick of evidence.
Raseclamid, you need to think... shallow... deep... whatever works for you, but this article jumps to so many conclusions if it had legs it would break them clean off.
Scientific American has become laughable with their absurd "reporting" of Global Warming stupidities. They are no longer a credible source of scientific information but are now spokesmen for politically inspired agenda with no debate or discussion. How low will they go?
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