SUMMER could result in 50 cities in the US under siege by the Zzika virus, as its needle-nosed host — the aedes aegypti mosquito — marches its way north with a warmer climate.

According to computer simulations run by the National Center for Atmospheric Research and the NASA Marshall Space Flight Center, the emerging springtime conditions will support low to moderate populations of the mosquito breed in southern US regions.

Wintertime remains too cold for the species — other than in Florida and southern Texas.

But aedes mosquitos appear happy to migrate as the weather warms.

Scientists have been studying the mosquito’s travel patterns in countries contending with Zika outbreaks.

Extrapolated to the US, the research team warns that cities in southern Florida and “impoverished” areas in southern Texas are particularly vulnerable.

But the threat doesn’t end there.

With the US experiencing abnormally warmer weather year-upon-year, the mosquito’s reach is already much further north than anticipated.

By April, the mosquito could be capable of marching into the Southeast US and some part of Arizona. By June, almost 50 cities will have the potential for moderate aedes mosquito populations.

DEADLY EQUATION

The authors of the study published in the journal PLOS Currents Outbreaks note that long-range forecasts for this summer point to a 40-45 per cent chance of warmer-than-average temperatures over most of the continental United States.

NCAR scientist Andrew Monaghan, the lead author of the study, says this could lead to aedes finding it comfortable in much of the South and East. However, above-normal temperatures would be less favourable for the species in the hottest regions of Texas, Arizona, and California.

But, on top of purely climatic factors, the researchers also studied other influences on the spread of Zika.

Key among them are travel from zika-affected areas, and the socio-economic conditions that may produce heightened exposure to mosquitos.

Despite today's headlines, I think best risk map of #Zika in #USA is from @simonihay on Aedes aegypti distribution pic.twitter.com/06QLoV0ygu — Dr. Peter J. Hotez (@PeterHotez) March 18, 2016

Miami, Houston and Orlando featured high on the scale of supporting the aegypi mosquito and exposure to travel from the 22 Latin American countries listed by the Centers for Disease Control and Prevention as being infected.

The US-Mexico border, however, was the highest transmission risk — with five times more people crossing into the US there than by air in all 50 cities.

“Those border areas, as well as other parts of the South where the mosquitoes are expected to be abundant, have a high percentage of households living below the poverty line ... Lower-income residents can be more exposed to mosquito bites if they live in non-air conditioned houses or have torn or missing screens they enable mosquitoes to enter their homes more easily,” a statement reads.

ON THE MARCH

The Zika virus was first discovered in Uganda in 1947. Since then it has spread only slowly — until it began to explode through the world’s tropical regions just a decade ago.

The virus reached Brazil just a year ago and has since steamrolled its way across Latin America and the Caribbean. Some 20 countries are now on the brink of pandemics.

While 80 per cent of sufferers suffer little more than cold-and-flu symptoms for less than a week, there appears to be a particular risk for those who contract the disease during pregnancy. Microcephaly, a birth defect producing an abnormally small head, can result.