climate change health

Climate change and West Nile virus

Amidst the talk of melting ice, rising seas and extreme weather, there are a few lesser known effects of climate change. One side to the crisis which gets less attention is the human health perspective.

I was reminded of this by the current news stories coming out of Texas. This week, Dallas is spraying insecticide from the air to try and kill off the mosquito population, in an effort to stop the spread of West Nile virus. It’s a disease that’s been known in Africa for decades, and has also appeared in plenty of other parts of the world over the years. It arrived in the US in 1999 and this year has been particularly bad, forcing officials in Dallas to declare a state of emergency.

West Nile virus thrives in warm conditions, as warm temperatures extend the mosquito breeding season. As the summer goes on there are more mosquitos and more carriers of the virus, so incidences of the virus tend to peak in late summer. As the climate changes there is a greater chance of warmer winters, and West Nile outbreaks become more likely.

Mosquitos generally do better in humid conditions, but in urban areas they can actually benefit from droughts. This is because mosquitos lay their eggs in stagnant water. During a drought, there is no rain to flush the drainage systems beneath the streets and wash the larvae away. Any little pools that remain in the gutters and drains become perfect breeding grounds. Texas has had a very dry year.

It would be wrong to make too direct a connection between the virus and climate change. Dallas is not facing a viral outbreak because of climate change. The point is that as the climate changes, the chances of better mosquito conditions become more and more likely – just as the odds of droughts and extreme weather shorten. Sending planes to spray the town with insecticides might deal with this particular outbreak, but protecting citizens in the long term means taking climate change seriously.


  1. I have just been to a lecture by an IPCC member and antarctic scientist, and he said that the Antarctic sea ice has been growing alarmingly since satellite records began back in 1979. It is now 800 000km2 above the 30 year normal for this time of year.

    Do you think that this good news (amongst the tide of bad) will help stop the spread of the west nile virus?

  2. As I understand it, Antarctica is gaining sea ice but losing land ice, so I’m not sure whether there’s good news there or not. And either way, I don’t think it would have any impact on the spread of the west nile virus. Is there a connection there that I’m missing?

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