The number of cases of Zika virus detected in Australia is now up to 76, with seven cases diagnosed this year in Far North Queensland.
The latest figures from the Federal Health Department show travellers arriving from countries such as Fiji, Tonga and Mexico have brought the virus to Australia.
Only five travellers came from Brazil.
Health authorities have said there is still no recorded cases of the virus spreading between people inside Australia.
But with wet season approaching in the north, public health authorities are preparing for a heavy mosquito breeding season.
Dr Richard Gair, the director of the Tropical Public Health Services in Cairns, said conditions were right for an outbreak.
“This time of year from November onwards is rainy season. The temperature goes up so we have more mosquitoes,” he said.
“The efficiency with which mosquito can transmit the virus is increased.
“We’ve never seen a Zika outbreak in Australia, but if we’re going to see a Zika outbreak we would expect it to be seen at the same time and the same place.”
Mosquitoes culled in tourist hotspots
The virus is of concern because it can cause a condition called microcephaly in the children of pregnant women.
It can be spread through mosquito populations and human-to-human sexual contact.
To protect the public, health authorities are killing off mosquitoes in places popular with international travellers, like hostels, testing more blood samples and running education programs about preventing mosquito bites.
“We’re also checking out areas where pregnant women might visit, such as schools, childcare centres and antenatal care centres because Zika is primarily a threat to pregnant women,” Dr Gair said.
“If we actually get a case then we go to the premises where that person has been and we look for mosquitoes.
“Then we go for approximately 100 metres around premises and do spraying to kill those mosquitoes.
“If we can get there early, we can kill all mosquitoes before they have a chance to become infectious.”
However, there is one complication for public health authorities that means preventing bites is the best approach.
“The majority of people who get it don’t have any symptoms at all,” Dr Gair said.
“If we get transmission via cases that aren’t unwell enough to go to their doctor, we aren’t going to know about it to do anything about it.
“Zika is a new emerging disease and we cannot say for definite how it will behave in north Queensland.”
Monitoring for Australian newborns
A sharp increase in the number of cases of microcephaly was what first alerted Brazilian authorities to the country’s Zika problem.
The Australia Paediatric Surveillance Unit at the Westmead Children’s Hospital in Sydney has just started monitoring all new cases of microcephaly in children under age one.
Director Professor Elizabeth Elliott said the surveillance unit would look at all the causes of the disease, which is characterised by a small skull and incomplete brain development.
“Microcephaly, or small head, usually implies that there’s a small brain so it’s usually associated with neuro-developmental problems and can be caused by a whole range of things, such as congenital infection,” she said.
“We were asked to conduct this study by the Federal Department of Health because when we looked at the prevalence, or frequency of microcephaly, we found that we really have very poor data in Australia.
“What the Zika virus has done has been to prompt us all over the world to say what is the normal expected frequency of microcephaly and if we see a blip in cases could it be due to say, the Zika virus.”