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WHO declares Zika virus a threat of ‘alarming proportions’

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Health authorities are on high alert to prevent a mosquito-borne virus linked to thousands of birth defects in South America getting a toehold in Australia.

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”.

Australia’s preparations come amid mounting international alarm over the rapid spread of the virus and fears it is linked to an increased incidence of serious birth defects including abnormally small heads and paralysis.

World Health Organisation Director-General Dr Margaret Chan said the virus was “spreading explosively” in South and Central America since being first detected in the region last year, and the WHO’s Emergency Committee has been convened to consider declaring the outbreak a Public Health Emergency of International Concern.

The virus, which is closely related to the dengue virus, was first detected in 1947, and there have only ever been 20 confirmed cases in Australia – six of them in 2015 alone, and all of them involving infection 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.

But there is no vaccine or treatment, apart from rest, plenty of fluids and analgesics, and Dr Chan said the speed of the virus’s spread and its possible link to serious birth defects meant the threat it posed had been elevated form mild “to one of alarming proportions”.

“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.

A causal relationship between Zika virus infection and birth malformations and neurological syndromes has not yet been established, but is strongly suspected.”

But there are concerns, yet to be scientifically verified, that the virus may cause microcephaly (small or under-developed brain) in unborn infants.

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.”

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