Zika Virus: Will It Spread And Can We Stop It?

Here is what we know:

:: What is the Zika virus?

The Zika virus takes its name from the Zika forest in Uganda, where it was first isolated from a rhesus monkey in 1947.

It is a flavivirus, a group of viruses that also cause yellow fever, dengue and West Nile fever. These diseases are spread by the Aedes mosquito. It is a daytime-biting insect - unlike the malaria mosquito, Anopheles, which bites at night.

About one in five infected people will develop relatively mild symptoms including a fever, muscle pain, red-eyes and a skin rash between three and 12 days after being bitten. There has been a rise in cases of paralysis due to the rare Guillain-Barre syndrome in countries affected by Zika but, at the moment, scientists are not certain that the virus is to blame.

The main concern is for the foetus, with a sharp rise in the number of babies born with microcephaly, an exceptionally small head and incomplete brain development.

:: Is the Zika virus contagious?

Zika is considered to be primarily spread by mosquitoes which inject the virus while feeding on a human's blood. It then multiplies in the human bloodstream and can be picked up by other mosquitoes that bite and feed.

But there have been reports of the virus being sexually transmitted from people who have travelled in Zika-affected areas to partners who have not.

The virus has also been found in semen. Scientists don't know how many sexually transmitted cases there are in South and Central America because mosquitoes are so common and are by far the most likely routed of the virus spreading. The virus is not airborne, so it is not spread from person to person like flu.

:: How long does the Zika virus last?

According to the US Centres for Disease Control, the Zika virus usually remains in the blood of an infected person for up to a week.

It will not cause infections in an infant that is conceived after the virus has disappeared from the blood. There is currently no evidence that Zika virus infection poses a risk of birth defects in future pregnancies.

:: How to prevent Zika virus?

There is no treatment or vaccine, so prevention is essential. The basic rules of mosquito avoidance are to wear long sleeved tops and trousers and to use insect repellents containing DEET.

The Aedes mosquito bites primarily between dawn and mid-morning, and then between mid-afternoon and dusk.

Because the risk is thought to be primarily to unborn babies, women are advised not to travel in affected countries if they are pregnant or planning to become pregnant.

Men who have travelled in affected countries should use condoms when they return home, if their partner is pregnant - for 28 days if they haven't had Zika symptom, for six months if they have.

:: How to test for Zika virus?

There are no commercially available diagnostic tests for Zika.

In the first week of the infection, genetic material from the virus can be detected with specialist techniques. In the latter stages antibodies can be detected.

:: Where will the Zika virus spread?

The virus is spreading fast.

The first case was in Brazil in May 2015. It now affects more than 30 countries. It's likely to affect every country in the Americas apart from Canada and Chile.

But it could spread further - either in the blood of travellers, or in mosquitoes stowed away in bags or cargo. The Aedes mosquito is found throughout the tropics and sub-tropics - as far north as southern Europe.