What about other diseases spread by mosquitoes, like West Nile?
West Nile virus is endemic in the United States and outbreaks are triggered by several factors, including the concentrations of culex mosquitoes, humans who are not immune, and birds who are not immune. (The virus builds up to higher concentrations in bird blood than in human blood, so mosquitoes tend to pick it up from them to give to humans.) Birds were also probably driven away from coastal Texas by Hurricane Harvey’s winds.
In 2005, in the wake of Hurricane Katrina, there was initially no increase in cases of West Nile virus or St. Louis encephalitis, which is also spread by mosquitoes, noted Dr. Peter J. Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston. But a year later, there was a surge in dangerous “neuroinvasive” West Nile disease in the affected regions of Louisiana and Mississippi: Cases of encephalitis and meningitis more than doubled. Researchers from Tulane University’s School of Public Health and Tropical Medicine speculated that more people were bitten that year because they were outside doing reconstruction work or living inside partially-destroyed houses that mosquitoes could invade easily.
What about disease transmission in shelters?
“The big thing I’m worried about is norovirus,” said Dr. Persse, Houston’s chief medical officer. “That’s the ‘cruise ship virus’ – with a lot of people in a small space, it can spread really quickly.”
In shelters, it can be hard to control. Health officials try to stop outbreaks by quickly taking the sick to separate rooms where they are given food and entertainment, there is no wait for toilets and the floors are washed frequently with bleach.
Dr. Persse’s medical teams are walking through shelters now looking for people vomiting. Shelter populations are thinning out as people return home or find other places to stay, so the danger is decreasing.
After Hurricane Katrina, 200,000 refugees ended up in 750 shelters in 18 states, and there were scattered outbreaks of various diseases, the C.D.C. said.