Like most public health scientists I am fascinated by the complicated relationship between the environment and disease. You build a military base somewhere and sexually transmitted diseases follow. You build a dam in Egypt and urinary schistosomiasis, a chronic debilitating disease that also predisposes to bladder cancer, entrenches itself in an area because infected workers are attracted from far away endemic areas. They work and often urinate in the water, seeding the shallows of rivers and lakes with schistosome eggs. When the eggs get into the snails, they germinate, the schistosome matures and eventually finds its way to humans by water contact.
In fact any vector borne disease can be affected by the environment in unexpected ways. Here I am including the social environment in the equation. Consider the current mortgage crisis in the US:
Foreclosures are increasing West Nile virus dangers because of stagnant swimming pools behind abandoned homes.
The foul pools are breeding grounds for mosquitoes, which can pass West Nile to humans and horses. The spike in mosquitoes comes earlier than the usual summertime appearance of the pest.
The Greater Los Angeles County Vector Control District got 288 service requests last month, nearly double the 145 in May 2007.
Agency spokeswoman Truc Dever says “all of the evidence is pointing to a very active West Nile season.” (AP)
West Nile fever is caused by a bird virus (sound familiar?). The birds are infected by mosquitoes who transfer the virus from bird to bird. The mosquitoes that bite birds are not usually the same as the ones that bite humans, but there are so-called bridge vectors, mosquitoes that bite both. Apparently it is these viruses the vector control folks are concerned about in the swimming pools. It remains to be seen if the pools and abandoned houses will have any significant effect on the transmission of West Nile disease. We still don’t understand the factors that make one season much worse than another for this disease. But it’s plausible.
West Nile infection has a broad spectrum of severity, from virtually asymptomatic to severe neurological infection with chronic disabilities or even a fatal outcome. So if the proposed effect of abandoned swimming pools is valid, it is reasonable to say that along with the other miseries of these foreclosures, we can add fatal disease to the toll.
Our world is interconnected in surprising and often hazardous ways.