Geneva/Sydney: The Zika virus linked to a microcephaly outbreak in Latin America could spread to Africa and Asia, with the world's highest birth rates, the World Health Organization (WHO) warned as it launched a global response unit against the new emergency.
The WHO on Monday declared an international public health emergency due to Zika's link to thousands of recent birth defects in Brazil.
"We've now set up a global response unit which brings together all people across WHO, in headquarters, in the regions, to deal with a formal response using all the lessons we've learned from the Ebola crisis," said Anthony Costello, WHO director for maternal, child and adolescent health.
"The reason it's a global concern is that we are worried that this could also spread back to other areas of the world where the population may not be immune," he told a news conference in Geneva on Tuesday.
"And we know that the mosquitos that carry Zika virus - if that association is confirmed - are present... through Africa, parts of southern Europe and many parts of Asia, particularly South Asia..."
Costello added the WHO was drafting "good guidelines" for pregnant women and mustering experts to work on a definition of microcephaly including a standardised measurement of baby heads.
"We believe the association is guilty until proven innocent," he said, referring to the connection drawn in Brazil between the Zika virus and microcephaly, a condition where babies are born with abnormally small heads.
"Mass community engagement" in areas with the mosquitos and their breeding grounds, and rapid development of diagnostic tools are essential to curbing the virus, as a vaccine may be years away, said Costello, a paediatrician.
Sanofi has launched a project to develop a vaccine against Zika, the most decisive commitment yet by a major vaccine producer to fight the disease.
The French drugmaker said on Tuesday its Sanofi Pasteur vaccines division would use its expertise in developing vaccines for similar viruses such as yellow fever, Japanese encephalitis and, most recently, dengue.
"Sanofi Pasteur is responding to the global call to action to develop a Zika vaccine given the disease's rapid spread and possible medical complications," said Nicholas Jackson, research head of Sanofi Pasteur, who is leading the new Zika vaccine project.
Two Australians were diagnosed with the Zika virus after returning home from travels in the Caribbean, a state health service said on Tuesday, confirming the first cases of the mosquito-borne virus in the country this year.
Officials also said that mosquitos carrying the virus had been detected at Sydney International Airport, but stressed that it was unlikely the virus would establish local transmission given the lack of large numbers of the Aedes Aegypti mosquitos.
The New South Wales (NSW) health department said the two Sydney residents were diagnosed with the Zika virus on Friday after returning to Australia from Haiti.
Formal diagnosis can take several weeks and the department did not disclose when the couple were tested. It said the pair had mild cases of the virus and had recovered.
"It is very unlikely that Zika virus will establish local transmission in NSW as the mosquitos that spread the infection are not established here - although they are found in some parts of north Queensland," Vicky Sheppeard, director of communicable diseases at NSW Health, said in a statement.
Earlier on Tuesday, the Department of Agriculture said it was imposing additional cabin spraying of insecticides on flights arriving into Sydney from Southeast Asia. The department said the step-up in procedures, which includes adding extra mosquito vector monitoring traps, followed the "recent detection" of Aedes Aegypti mosquitos at Sydney airport.
"These measures are undertaken to prevent these mosquitoes establishing breeding populations in Australia, thereby preventing the potential for the local spread of these diseases," the department said in a statement.
Queensland state in the north of the country is on high alert for any entry of the disease from Australia's Asian neighbours.
Thailand public health ministry said that Thailand should not worry about the Zika virus. Thailand is the worst-hit country in Southeast Asia, with an average of five cases a year since 2012, according to the Ministry of Public Health.
Thailand has confirmed one case of the virus this year.
In addition, last month, Taiwan reported one case of Zika infection in a man from Thailand after he set off a temperature scanner at Taiwan's Taoyuan International Airport.
"Thais should not worry. Thailand has no outbreak of this disease," the Ministry of Public Health said in a statement.
"We have asked everyone to monitor and prepare measures to look after this disease... Thais should not panic. Mostly if patients get this disease they recover," the ministry said.
Neighbouring Malaysia and Singapore have said they are at high risk for the spread of Zika if the virus is imported.
Thailand's public health ministry has said there was "no technical evidence" of in-built immunity to Zika in Thailand.
"I ask you to have confidence in Thailand's surveillance system," Amnuay Gajeena, director-general of the Disease Control Department, said in a statement.
The health ministry has asked members of the public to help eliminate mosquitos around their homes and in their communities and has advised those travelling back from Zika-affected areas to report any symptoms.