Zika virus explained: Where is it found, what are the dangers and symptoms, how do you prevent it spreading?

A traveller infected with Zika returns to their home country, or travels to another country with a population of Aedes mosquitos, one of those mosquitos dips its proboscis into the traveller's bloodstream and the stage is set for a local outbreak.

According to the University of Sydney's department of medical entomology, Aedes aegypti mosquitos are found in Australia only in Queensland, predominantly in coastal areas, but they have previously been detected in WA, NT and southern NSW.

So far Zika has not been found in any of these Australian mosquito populations but at the beginning of September the Department of Health reported 44 Australians had tested positive for Zika contracted overseas, including one pregnant woman.

See also: Zika virus: What travellers need to know

More insidious still, anyone infected might not even be aware that they carry Zika. Most will show no symptoms.

Those who do will probably experience fever, rashes, joint and muscle pain and conjunctivitis. These symptoms might last only a few days.

However, for pregnant women the implications for their unborn child are far more serious.

Another way that Zika can be transmitted is through sex.

In June the World Health Organisation reported mounting evidence that sexual transmission of Zika virus is possible and more common than previously assumed.

To the end of August, sexual transmission of Zika had been reported in 11 countries, including New Zealand but not Australia.

On the basis of this new evidence WHO suggests that anyone returning from an area with active Zika transmission, regardless of whether or not they show any symptoms of Zika, should practice safe sex for six months.

The other suggested option is abstinence. Also for six months.

Several million Australians will visit countries where Zika is active during the next 12 months. If they were to follow the WHO guidelines Australia would suffer a major baby drought, although it might be boom time for the relationship counselling industry.

At the moment there is no test that can reliably detect Zika. The US Centers for Disease Control and Prevention suggests that a blood or urine test can confirm a Zika infection.

However, the CDC also cautions that a negative test does not exclude Zika.

For anyone who displays symptoms, Zika virus RNA can sometimes be detected early in the course of illness, according to the CDC.

Sometimes is not good enough to rule it out, and therefore the injunction against unprotected sex.

There is no vaccine or specific treatment against the Zika virus. Treatment is directed at alleviating symptoms.

All the health authorities are stressing prevention. Anyone travelling to an area where the Zika virus is present is advised to cover exposed skin day and night as far as possible, use mosquito repellents, wear clothing treated with insecticide and sleep in a screened or air conditioned room, under a net if mosquitos may be present. Which suddenly makes a holiday in Scandinavia look like a compelling prospect. Provided there's no local hanky-panky involved.

For a list of countries with active Zika transmission see the US Centers for Disease Control and Prevention page:http://www.cdc.gov/zika/geo/active-countries.html

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