Doctors David Baud and Alice Panchaud, specialists in women’s health and pregnancy, announced the register in an article published in international journal The Lancet ID on Tuesday.

The only way to better understand the Zika virus – which is thought to cause birth defects in unborn babies – is to launch a large study, said the pair in a statement by CHUV.

“The idea came to us as we remarked that a number of questions remain unanswered about this virus and the only way to answer them is to have a lot of cases,” said Baud.

Until now, the only papers published on the virus only focus on a few cases at the time without having ruled out other causes of brain defects, said the statement.

For the register to work, CHUV needs the cooperation of doctors in affected countries, so the researchers have sent requests to 4,000 obstetricians around the world.

Baud’s laboratory at CHUV is already studying the virus and the ways in which it can infect human cells.

“If we understand how the virus infects, we can better prevent this infection, either by medicine or by a vaccine,” said Baud.

Declared a world health emergency and thought to have affected 60 countries to date, the Zika virus is spread by Aedes aegypti mosquitoes in Latin America.

Most of the time the infection is benign and in 60-80 percent of cases it causes no symptoms.

However in infected pregnant women the virus is thought to cause serious birth defects in the foetus, including microcephaly, a brain defect where the baby’s head is smaller than normal.

There is currently no vaccine against Zika, so pregnant women and those who wish to conceive in the near future are advised against travelling to affected regions, as are their partners, over fears the virus can be sexually transmitted.

Speaking to news agencies, Baud said the research that comes out of the register could answer the question of whether contracting the virus through sexual intercourse is as dangerous to pregnant women as becoming infected by a mosquito.

Switzerland’s health authorities have registered 28 cases of Zika since the start of the year.

In 18 of those cases people had returned from Latin American countries.