An outbreak of West Nile virus in the U.S. has become so serious that the city of Dallas, Texas has declared a state of emergency and ordered aerial spraying to begin tonight.
The Centers for Disease Control and Prevention report that 693 cases of West Nile have been reported in 43 states so far this year, with the concentration of cases in Texas. That state, according to the CDC, has had 336 cases in 2012; Mississippi has the next highest caseload, with 59. There have been 26 deaths.
The CDC says this is the biggest number of reported year-to-date West Nile cases since 1999, when the disease was first noted in the U.S.
Of the nearly 700 cases, 59 percent were neuroinvasive diseases such as meningitis or encephalitis, and the rest were non-neuroinvasive. West Nile is almost always transmitted by mosquitos, which become infected after biting infected birds. While most people will have no reaction, serious symptoms include fever, headache, skin rash, body aches and vomiting.
Mike Raupp, an entomology professor with the University of Maryland, said on CBS This Morning that the high case numbers can be blamed on a combination of infected birds, large numbers of mosquitos, high temperatures and wet conditions. He called the current spate of West Nile cases “quite disturbing.”
But aerial spraying of mosquito-killing pesticide may carry its own risks, and some Dallas residents are worried about the ramifications of that.
Kelly Nash, a Dallas resident who works for an environmental consulting firm, told USA Today, “I'm concerned that we're breeding resistant mosquitoes that next time will have Dengue fever or something worse.”
On CBS, Raupp said the benefits of spraying outweigh the risks, adding that the pesticides, usually pyrethroids, are “relatively safe materials.”
The Environmental Protection Agency recently updated its information on pyrethroids and pyrethrins, insecticides it says are used in more than 3,500 registered products.
Pyrethroids are synthetic forms of pyrethrins, which come from chrysanthemums and cause paralysis and eventually death in insects.
In its most recent analysis, the EPA found that the insecticides don’t post a risk to children or adults, although they’re extremely toxic to fish and other aquatic creatures and may pose a risk to organisms that live in sediment.
Some studies suggest there may be health risks linked with pyrethroids. A 1999 study in the journal Environmental Health Perspectives looked at the effects of pythrethoid compounds on a human breast cancer cell line, and found that pyrethroids may act as hormone disruptors. A 2009 study in Public Health Reports examined pesticide poisoning surveillance data for four years in Oregon and Washington and discovered that although most pyrethrin and pyrethroid poisoning cases were mild, some adverse reactions occurred.
Do the benefits of insecticide spraying outweight the risks when it comes to controlling West Nile virus? Let us know in the comments.