In a new study published looked at 50 U.S. cities where the weather could support Aedes aegypti (the yellow fever mosquito that spreads Zika and other dangerous diseases) in warmer months.
Cities at Risk
Yellow cities are low-risk, orange are moderate, and red are high. The size of the dot over the city represents how many travelers from current Zika-affected countries come to the city on average each month. And the gray zone represents the area where Aedes aegypti has been observed in earlier years.
How Risk Was Calculated
To determine which cities would be most at risk and when, the researchers examined a number of factors:
- The estimated abundance of Aedes aegypti mosquitoes per square meter of standing water, based on their life cycle and the historical meteorological conditions in each city (from 2005 to 2015)
- The number of travelers arriving in those cities from Latin American countries currently affected by Zika (although the researchers do note that some people on those flights may have just connected through a Zika-affected country)
- Previous cases of locally transmitted dengue and chikungunya, two other diseases transmitted by Aedes aegypti
- Percentage of households in each city living under the poverty line, which makes people less likely to have air conditioning (Aedes aegypti doesn’t survive well in air-conditioned buildings), safe water, and good sanitation.
- Irregular garbage collection in some areas may also provide opportunities for the bug to breed.)
- Observations from 1960 to 2014 of the mosquito’s maximum geographic range
Expected To Spread
Based on their estimates, this is how the year plays out in terms of highest risk for abundant Aedes aegypti populations:
Mosquito Spraying Helps Prevention
It’s also worth noting that the models don’t account for mosquito-control methods—so there’s still plenty of room to bring this risk down by spraying for adult mosquitoes, using larvicides, and eliminating mosquito-breeding sites, particularly standing water.