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15 Apr 2016

The United States’ Centers for Disease Control and Prevention has declared that the Zika virus is a cause of microcephaly and other severe foetal brain defects, confirming long-held suspicions about the infection’s link to serious neurological disorders.

As the US gears up for outbreaks of the potentially deadly virus, the CDC has reported that an accumulation of evidence proves Zika can cause birth defects and pregnant women living in or travelling to areas of where it is prevalent should strictly follow steps to avoid mosquito bites and prevent sexual transmission of the virus.

“This study marks a turning point,” CDC Director Dr Tom Frieden said. “It is now clear that the virus causes microcephaly. We’ve now confirmed what mounting evidence has suggested, affirming our early guidance to pregnant women and their partners to take steps to avoid Zika infection.”

The CDC report, published in the New England Journal of Medicine, said its conclusion was not based on any one discovery but rather an accumulation of evidence from a number of recently published studies and a careful evaluation using established scientific criteria.

The CDC announcement came as the Australasian Society for Infectious Diseases reminded GPs to be on heightened alert for tropical diseases in patients with febrile illnesses – particularly those who have recently travelled overseas.

Society President Professor Cheryl Jones said serious tropical diseases including Zika, multi-drug resistant malaria and dengue were endemic in many overseas destinations popular with Australians, including Thailand, Vietnam, Myanmar, Laos and Cambodia, and there was also a local outbreak of dengue in northern Queensland.

“There has never been a more critical time for Australian health professionals to get up to speed with developments in tropical medicine,” Professor Jones said. “With malaria resistance growing and no antiviral treatment available for dengue, Zika and other mosquito-borne viruses, it is imperative that Australian doctors are able to identify these diseases and refer patients swiftly.”

Her warning came as a senior US public health official, Dr Anne Schuchat, told a White House briefing that the virus “seems to be a bit scarier than we initially thought”.

Dr Schuchat, who is a deputy director of the US Centers for Disease Control and Prevention, said that initially it was thought the species of mosquito primarily associated with carrying the disease was only present in about 12 states, but that had now been revised up to 30 states.

Authorities are particularly concerned about the US territory of Puerto Rico, where they fear there may be hundreds of thousands of infections, but the speed of the disease’s spread has them concerned it may soon appear in continental US as temperatures rise.

“While we absolutely hope we don’t see widespread local transmission in the continental US, we need the states to be ready for that,” Dr Schuchat said.

While the Zika virus has been documented in 61 countries since 2007, the World Health Organization said its transmission has really taken off since it was first detected in Brazil in May last year, and it is now confirmed in 33 countries in Central and South America, as well as 17 countries and territories in the Western Pacific, including New Zealand (one case of sexual transmission), Fiji, Samoa, Tonga, American Samoa, Micronesia and the Marshall Islands.

Its appearance has been linked to a big jump in cases of microcephaly, Guillian-Barre syndrome (GBS) and other birth defects and neurological disorders, and the WHO said that there was now “a strong scientific consensus” that the virus was the cause.

In Brazil, there were 6776 cases of microcephaly or central nervous system malformation (including 208 deaths) reported between October last year and the end of March. Before this, an average of just 163 cases of microcephaly were reported in the country each year.

The WHO reported 13 countries or territories where there has been an increased incidence of GBS linked to the Zika virus. French Polynesia experienced its first-ever Zika outbreak in late 2013, during which 42 patients were admitted to hospital with GBS – a 20-fold increase compared with the previous four years. All 42 cases were confirmed for Zika virus infection.

Similar increases in the incidence of GBS cases have been recorded in other countries where there is Zika transmission, including Brazil, Colombia, El Salvador, Venezuela, Suriname and the Dominican Republic.

Scientists have also detected potential links between the infection and other neurological disorders. In Guadeloupe, a 15-year-old girl infected with Zika developed acute myelitis, while an elderly man with the virus developed meningoencephalitis. Meanwhile, Brazilian scientists believe Zika is associated with an autoimmune syndrome, acute disseminated encephalomyelitis.

Scientists worldwide are working to develop a vaccine for the virus, and an official with the US National Institute of Allergy and Infectious Diseases said initial clinical trials of a vaccine might begin as soon as September.

Meanwhile, research on other aspects of Zika, including its link with neurological disorders, sexual transmission and ways to control the mosquitos that spread the disease is being coordinated internationally.

So far, the only confirmed cases of Zika in Australia have involved people who were infected while travelling overseas, and authorities are advising any women who are pregnant or seeking to get pregnant to defer travelling to any country where there is ongoing transmission of the virus.

Adrian Rollins

Published: 15 Apr 2016