It Loves Our Cities

Federal health officials urged pregnant women to stay away from a Miami neighborhood where they have discovered additional cases of Zika infection — apparently the first time the Centers for Disease Control and Prevention has advised people not to travel to a place in the continental United States.Florida officials said the number of Zika cases caused by local mosquitoes had risen to 14 from the four announced early August, 2016: 12 men and two women. They declined to say whether either woman was pregnant. All of the cases have been in one neighborhood. Health officials said they still did not expect the number of local cases to grow into anything comparable to the epidemic that has raged across Latin America in recent months. This is not some jungle-dwelling insect that rarely comes into contact with people. It is one of those animals, like cockroaches, pigeons and urban foxes, that thrives in built-up areas. It does not need natural water sources to breed as it can lay eggs in the small and plentiful pools of stagnant water, such as gutters or flower pots, found in cities.

Mosquito Larvae Thrive in Stagnant Water

Cities like Singapore have big problems with the mosquito. Prof Uriel Kitron, from Emory University, said: "Aegypti is really adapted well for urban areas. "It is becoming more and more of an urbanised world and aegypti thrives -

Geovano Silva Holds his Son Gustavo Henrique

Brazil is an Extreme Example Going from 20% to 80% Urban in 70 years."  There's also plenty of food - us.  The Center for Disease Control (CDC) has developed interim guidelines for health care providers in the United States caring for pregnant women during a Zika virus outbreak. These guidelines include recommendations for pregnant women considering travel to an area with Zika virus transmission and recommendations for screening, testing, and management of pregnant returning travelers. Updates on areas with ongoing Zika virus transmission are available online at http://wwwnc.cdc.gov/travel/notices/.

They Harbour a Bunch of Diseases

Dengue fever is also spread by mosquitoes Zika is currently getting all the attention, but Aedes aegypti has long been known as the yellow fever mosquito. Yellow fever is a viral disease that can cause jaundice, bleeding and multiple organ failure in some cases. And 390 million people are infected with the dengue virus each year, largely as a result of bites from Aedes aegypti. Chikungunya, another virus causing alarm as it expands around the world, is also spread by the insects. They do it by biting someone who is infected and then biting someone else.  Only the females bite and they love human blood.

Up to Four Million Zika Cases Predicted

Zika Could Become Pandemic

Zika Virus Cycle

Both the male and female mosquitoes feed off plant nectar. However, the females need a blood meal in order to produce eggs. Two traits make them especially good at spreading disease. First they feed almost exclusively on humans, so if they pick up a disease from one person, they are likely to pass it on with their next bite. Other mosquitoes are less efficient spreaders as they feed off a variety of animals. These particular blood suckers also drink little and often. Rather than gorge their entire meal from one person and running the risk of being swatted they graze from multiple people making it easier to spread disease. They are also active during the day so bed nets are less effective.

It's a Lazy Hitch-Hiker

"They're amazing hitch-hikers, but they're lousy flyers," argues Prof Kitron. The mosquitoes that carry malaria can fly for miles, but Aedes aegypti is pretty lazy by comparison. It stays close to the area where it was born and 100m is a long way for it to fly. Prof Kitron says: "But they're good at catching rides, their whole life cycle can take place in the water in a boat." So despite its short flying distances it has managed to conquer the world.

It Has a Cousin that Could Bring Zika to Cooler Regions of the World 

Aedes aegypti lives in tropical and subtropical climates - it is why experts are worried Zika could spread across the Americas, a huge swathe of Africa as well as India and China. However, the similar Aedes albopictus - or Asian Tiger mosquito - likes cooler more temperate areas.