A state-by-state report on the recorded incidence of West Nile Virus issued by the Centers for Disease Control on Aug. 14 suggests the spread of the potentially debilitating disease, which first appeared in New York State in 1999, may be linked to climate warming. 
People who work outdoors and are exposed to the mosquitoes that transmit the disease should take notice. The spread of the West Nile Virus poses a growing risk for the construction industry. The pattern of increasing incidence seems to go hand-in-hand with this year's sustained hot weather in the heartland and the California Central Valley.
West Nile virus (WNV) Neuroinvasive Disease Incidence reported in 2012  by
As of August 14, 2012

The data is collected by ArboNET, a national electronic surveillance system established by CDC to assist states in tracking West Nile virus and other mosquito-borne viruses.

A total of 693 cases were recorded, parsed into the more serious neruoinvasive disease cases, which compromise the nervous system (406 cases), and the nonneuroinvasive cases (287), which don't. 
The report cautions that the high proportion of the most serious cases among those reported reflects a reporting bias, because serious cases are more likely to be reported than mild ones. It notes that other, population-based surveys indicate that among all people who become infected with West Nile virus, including people with asymptomatic infections, less than 1% will develop the most severe conditions.
California reported 23 cases of both classes of the disease, South Dakota 37, Oklahoma 49, Louisiana 52, Mississippi 59, and Texas, 336, of which 200 were of the more severe condition.  
The report states that Nonneuroinvasive disease cases are typically less severe and show no evidence of neuroinvasion -- direct impact on the nervous system. West Nile fever is the primary example. West Nile fever is considered a notifiable disease, but the number of cases reported may be limited by whether persons affected seek care, whether laboratory diagnosis are ordered and the extent to which cases are reported to health authorities by diagnosing physicians.
Neuroinvasive disease cases are more severe.  According to the report, those cases affect the nervous system and include encephalitis, which is an inflammation of the brain, meningitis which is an inflammation of the membrane around the brain and the spinal cord and acute flaccid paralysis which is an inflammation of the spinal cord that can cause a sudden onset of weakness in the limbs and/or breathing muscles. 
The New York Times, in an article August 15, connected the dots on a likely link between a warm winter, a blazing summer and the areas with higher incidence of the disease. 
The CDC report doesn't parse that data by occupation, but any serious disease that is transmitted by the mosquitoes that bedevil people who work outdoors may also affect the construction industry disproportionately from the rest of the population. 
During the invasion of Iraq in 2003, I met an English Army sanitation engineer attached to the U.S. Army's Third Infantry Division's combat engineers who were fighting around Baghdad. His task, right in the middle of a shooting war, was to do what he could to make bases and encampments safer for the soldiers by reducing natural hazards. He was focused, at least initially, on protecting troops from pests carrying parasites and diseases. 
If that is a high enough priority to warrant a dedicated engineer on a battlefield, then it may be that the next engineers we need to see on jobsite startups are environmental engineers tasked with improving site conditions to reduce workers' exposure to hazards such as the mosquitoes that transmit the virus West Nile.