SYDNEY (REUTERS) - The Australian authorities stepped up the fight against Zika in the north of the country on Thursday (Feb 25), spraying homes and businesses near a hotel after a guest tested positive for the disease and mosquitoes carrying the virus were detected.

The Queensland state health authorities said the man did not contract the disease locally but during a trip to South America.

However, the mosquito that carries the Zika virus, Aedes aegypti, was found breeding around his hotel in Rockhampton, 640km north of the state capital of Brisbane.

The state's acting chief health officer said the spraying was a precaution aimed at preventing mosquitoes from spreading the man's infection. Health officials were also checking on nearby homes to make contact with any pregnant women.

The Aedes aegypti mosquito is endemic to north Queensland and has also been found in some towns in the state's central and south-west. The state is on high alert for any entry of the disease from Asian and Pacific neighbours and testing in the far tropical north will begin on March 1.

The World Health Organisation declared the Zika outbreak an international health emergency on Feb 1, citing a "strongly suspected" relationship between Zika infection in pregnancy and microcephaly, a condition marked by abnormally small head size that can result in developmental problems.

The US Centers for Disease Control and Prevention says the virus is being actively transmitted in 30 countries, mostly in the Americas.

Much remains unknown about Zika, including whether the virus actually causes microcephaly. Brazil is investigating the potential link between Zika infections and more than 4,300 suspected cases of microcephaly.

There is no vaccine or treatment for Zika. An estimated 80 per cent of people infected have no symptoms, making it difficult for pregnant women to know whether they have been infected.