Potential Zika risk estimated for 50 US cities: Study

Key factors that can combine to produce a Zika virus outbreak are expected to be present in 50 US cities during peak summer months, a new study has warned.

The Aedes aegypti mosquito, which is spreading the virus in much of Latin America and the Caribbean, will likely be increasingly abundant across much of the southern and eastern US as the weather warms, according to the study led by experts at the National Centre for Atmospheric Research (NCAR) in US.

Summertime weather conditions are favourable for populations of the mosquito along the East Coast as far north as New York City and across the southern tier of the country as far west as Phoenix and Los Angeles, according to computer simulations conceived and run by researchers at NCAR and the NASA Marshall Space Flight Centre.

 

Spring and fall conditions can support low to moderate populations of the Aedes aegypti mosquito in more southern regions of its US range. Wintertime weather is too cold for the species outside southern Florida and southern Texas, the study found.

Researchers analysed travel patterns from countries and territories with Zika outbreaks and found that cities in southern Florida and impoverished areas in southern Texas may be particularly vulnerable to local virus transmission.

"This research can help us anticipate the timing and location of possible Zika virus outbreaks in certain US cities," said Andrew Monaghan from NCAR.

"While there is much we still do not know about the dynamics of Zika virus transmission, understanding where the Aedes aegypti mosquito can survive in the US and how its abundance fluctuates seasonally may help guide mosquito control efforts and public health preparedness," Monaghan said.

"Even if the virus is transmitted here in the continental US, a quick response can reduce its impact," added Mary Hayden from NCAR.

Although the study does not include a specific prediction for this year, researchers note that long-range forecasts for this summer point to a 40-45% chance of warmer-than-average temperatures over most of the continental US.

This could lead to increased suitability for Aedes aegypti in much of the south and east, although above-normal temperatures would be less favourable for the species in the hottest regions of Texas, Arizona, and California, Monaghan said.

Even if Zika establishes a toehold in the mainland US, it is unlikely to spread as widely as in Latin America and the Caribbean. This is partly because a higher percentage of Americans live and work in air-conditioned and largely sealed homes and offices, he said.

The findings were published in the journal PLOS Currents Outbreaks.