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Over the past week, twenty-eight people in the US have died from West Nile Virus as the number of cases rose from 693 from 390 over a one week period, a USA Today article reports this morning.  

While the virus has been reported in several states, Texas is currently most seriously impacted,  with sixteen deaths and 381 cases reported so far this summer.

Last Friday, for the first time in over five decades, the aerial spraying of insecticides was initiated in Dallas County after nearly 90 cases of the vector borne disease were reported.

Climate change in the US, which is causing hotter summers, and warmer winters and springs, is causing the uptick in West Nile, experts report. And conditions are expected to worsen.
The CDC reports West Nile Virus (WNV) has reached such proportions in the US it is currently considered a "seasonal epidemic."  Only one in 150 cases, however, become serious, life threatening illness, characterized by high fevers, coma, tremors, convulsions, numbness and paralysis.  

About one in 150 people infected with WNV will develop severe illness. The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent.
By extending the length of the mosquito breeding season and decreasing the amount of time it takes mosquitoes to reach their adult, biting stage, warmer weather means more biting mosquitoes longer. Moreover, increasing temperature speeds multiplication of the virus within insects, so mosquitoes in warmer climates have a greater viral load, making them more likely to infect humans.

Increased precipitation was also correlated with higher rates of West Nile Virus infection. A single, heavy rainstorm resulting in two or more inches of rain increased infection rates by 33%, while smaller storms had less of an effect on infection rates. Heavier rainfall events can increase disease prevalence by creating pools of water in which mosquitoes can breed and by increasing humidity, which stimulates mosquitoes to bite and breed. Total weekly rainfall had a smaller but significant effect on West Nile Virus infections, with an increase of 0.75 inch of rain/week increasing the number of infections by about 5%.

Warmer, wetter weather patterns might expand the niches of the mosquito species that carry West Nile Virus. In California, for instance, several mosquito species carrying the West Nile Virus have extended their ranges into higher elevations and coastal areas as temperatures have warmed. Changing weather patterns might also affect certain species of birds that are reservoirs for West Nile Virus. For example, droughts can push bird populations into urban areas, making West Nile Virus outbreaks in human populations more likely. Soverow, J.E., G.A. Wellenius, D.N. Fisman, and M.A. Mittleman. 2009. Infectious disease in a warming world: How weather influenced West Nile Virus in the United States (2001-2005). Environmental Health Perspectives. Online 16 March 2009 DOI: 10.1289/ehp.0800487

The CDC provide the following tips to prevent infection:

    •When you are outdoors, use insect repellent containing an EPA-registered active ingredient. Follow the directions on the package.
    • Many mosquitoes are most active at dusk and dawn. Be sure to use insect repellent and wear long sleeves and pants at these times or consider staying indoors during these hours.
   •  Make sure you have good screens on your windows and doors to keep mosquitoes out.
    • Get rid of mosquito breeding sites by emptying standing water from flower pots, buckets and barrels. Change the water in pet dishes and replace the water in bird baths weekly. Drill holes in tire swings so water drains out. Keep children's wading pools empty and on their sides when they aren't being used.

Climate Change and Health

photo
Chart by By zoï environment network

Climate change ticks ever closer
September 01, 2007, Toronto, Canada (Toronto Star/Canada) - The Leslie Street Spit is North America's most remarkable public urban wilderness. On the Leslie Street Spit, signs of global warming are being picked right from the feathers of migratory birds. And the ticks now spreading north carry with them the spectre of Lyme disease.

Health impacts of climate change
August 24, 2007, Quezon City, The Philippines (ABS-CBN Interactive/The Philippines) - …..Global warming can also increase the spread of infectious diseases, especially those that only appear in warm areas. Warmer temperatures could also result in a substantial increase in the geographical ranges of mosquitoes and other insects, thereby enabling these insects to spread diseases even farther. Diseases like malaria, dengue fever, yellow fever, and encephalitis are already experiencing a resurgence worldwide. As temperatures increase, the quality and quantity of drinking water could decrease as water source all over the globe become threatened by drought. Health disorders related to environmental and water contamination by bacteria, viruses, and parasites like diarrhoea, cholera, typhoid, and hepatitis ‘A’ could also increase.

 
Climate change affects the fundamental requirements for health – clean air, safe drinking water, sufficient food and secure shelter.
    The global warming that has occurred since the 1970s was causing over 140 000 excess deaths annually by the year 2004.
    Many of the major killers such as diarrhoeal diseases, malnutrition, malaria and dengue are highly climate-sensitive and are expected to worsen as the climate changes.
    Areas with weak health infrastructure – mostly in developing countries – will be the least able to cope without assistance to prepare and respond.
    Reducing emissions of greenhouse gases through better transport, food and energy-use choices can result in improved health.WHO
Resources
Changes in the Incidence of Vector-borne Diseases Attributable to Climate Change
CDC: Statistics, Surveillance, and Control Archive
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