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02 Feb 2016

The World Health Organisation has upgraded Latin America’s Zika virus outbreak to a public health emergency as Australian health authorities have been put on high alert to prevent the mosquito-borne infection, linked to thousands of birth defects, getting a toehold in Australia.

At a special meeting overnight, the WHO’s Emergency Committee considered that a “strong association” between Zika virus infections and serious congenital birth defects warranted declaring the rapidly spreading outbreak in South and Central America a Public Health Emergency of International Concern.

Acting on the recommendation, WHO Director-General Dr Margaret Chan said that although a causal relationship between Zika virus infection in pregnancy and microcephaly (small or under-developed brain) was not yet scientifically proven, it was “strongly suspected”.

“After a review of the evidence, the Committee advised that the recent cluster of microcephaly cases and other neurological disorders reported in Brazil, following a similar cluster in French Polynesia in 2014, constitutes an ‘extraordinary event’ and a public health threat to other parts of the world,” Dr Chan said.

In declaring a health emergency, the WHO has urged a coordinated international response to the virus threat, including improved surveillance of infections and the detection of congenital malformations, intensified mosquito control measures, and the expedited development of diagnostic tests and vaccines.

Though there is no evidence the Zika virus, which health experts suspect has infected millions in Brazil and surrounding countries in recent months, has been transmitted in Australia, authorities are concerned about the possibility someone infected with the disease overseas may travel to central and northern Queensland, where mosquitos capable of carrying the disease are found.

“There is very low risk of transmission of Zika virus in Australia, due to the absence of mosquito vectors in most parts of the country,” the Health Department said, but added that “there is continuing risk of Zika virus being imported into Australia…with the risk of local transmission in areas of central and north Queensland where the mosquito vector is present”.

Dr Chan said the virus was “spreading explosively” in South and Central America since being first detected in the region last year, and the prevalence of the mosquito capable of transmitting the virus, together with the fact that there is no vaccine or treatment, and no population immunity in newly-infected countries, were all causes for serious concern about the outbreak.

The virus, which is closely related to the dengue virus, was first detected in 1947, and there have only ever been 23 confirmed cases in Australia, all of them involving infection overseas.

So far this year, there have been just two confirmed cases – both in New South Wales and involving travellers from Haiti.

The Health Department said tere was currently "no practical mechanism" to detect the virus in travellers arriving from overseas.

Only about 20 per cent of those infected with the Zika virus show symptoms, and the disease itself is considered to be relatively mild and only lasts a few days.

“The level of alarm is extremely high,” Dr Chan said. “Arrival of the virus in some places has been associated with a steep increase in the birth of babies with abnormally small heads and in cases of Guillain-Barre syndrome.

In Brazil, a four-fold increase in the number of cases of microcephaly last year coincided with widespread outbreaks of the Zika virus, increasing suspicions of a link.

An investigation by the Brazil Ministry of Health found that of 35 cases of microcephaly recorded in a registry established to investigate the outbreak, 74 per cent of mothers reported a rash illness during their pregnancy. More than 70 per cent of the babies were found to have severe microcephaly, and all 27 that underwent neuroimaging were found to be abnormal.

“The possible links, only recently suspected, have rapidly changed the risk profile of Zika, from a mild threat to one of alarming proportions,” Dr Chan said. “The increased incidence of microcephaly is particularly alarming, as it places a heart-breaking burden on families and communities.”

Despite the threat, the WHO said there was no public health justification for restrictions on travel or trade.

Nonetheless, the Department of Foreign Affairs and Trade has issued a travel advisory recommending that pregnant women considering travelling to countries where the Zika virus is present to defer their plans.

“Given possible transmission of the disease to unborn babies, and taking a very cautious approach, pregnant women should consider postponing travel to Brazil or talk to their doctor about implications,” the Department said.

The Brazil outbreak has drawn particular attention given that hundreds of thousands of athletes, government officials and tourists are expected to travel to the country later this year for the Olympic Games.

DFAT has issued similar travel advice for all 23 countries where the virus has been identified - almost all of them in Southern or Central America, except for the Pacific island nation of Samoa and Cape Verde, off the north-west African coast.

All other travellers are advised to take precautions to avoid being bitten by mosquitos, including wearing repellent, wearing long sleeves, and using buildings equipped with insect screens and air conditioning.

The Health Department has issued advice for clinicians to consider the possibility of Zika virus infection in patients returning from affected areas, and said authorities were ready to act if it appeared in areas where mosquitos capable of transmitting it were present.

“In the event of an imported case in areas of Queensland where the mosquito vector is present, health authorities will respond urgently to prevent transmission, as they do for dengue,” the Department said.

Adrian Rollins

 


Published: 02 Feb 2016