The Zika virus owes its name to the Zika Forest, which is situated next to an inlet of Lake Victoria, not far from Entebbe in Uganda. The 25 hectares (62 acres) of tropical forest is a protected zone and it is used only for scientific research.

Zika means "overgrown" in the local Luganda language and is a rich hunting ground for scientists tracking down mosquito borne-viruses.

15-year-old Ester Kilabo is the forester's daughter. On her excursions into the forest she collects mushrooms, wild berries, figs and mosquito larvae. She points to a 36 meter (120 foot) steel tower, which looks a bit like a telecommunications mask with a ladder attached and she starts to climb.

"Here at the top," she tells DW, "the scientists from the Uganda Virus Research Institute have placed four tins of water and this is where the mosquitoes lay their eggs."

Ester scrambles up the tower every Wednesday to collect the four tins and hand them over to the scientists. The virus research institute is based in nearby Entebbe. This is where Uganda's virologists have been studying the world's most dangerous viruses, Ebola, Marburg, yellow fever and Zika for decades.

No treatment or vaccine

Zika is transmitted to people through the bite of infected female mosquitoes. The World Health Organization (WHO) says there is a strong scientific consensus that Zika can cause the birth defect microcephaly in babies, a condition defined by unusually small heads that can result in developmental problems. Brazil has confirmed over 1,000 cases of microcephaly since the outbreak started.

The WHO also said Zika, for which there is no treatment or vaccine, could cause Guillain-Barre syndrome, a rare neurological disorder that can result in paralysis.

The health agency also says sexual transmission of Zika is relatively common and it has advised pregnant women not to travel to areas affected by the ongoing outbreaks.

Virologists encountered Zika for the first time in Uganda in 1947 during research into yellow fever.

"Blood samples were collected and brought to the lab and it was identified that actually a new virus was appearing," Julius Lutwama, virologist at the Uganda Virus Research Institute, told DW.

The virus was identified in rhesus monkeys. People were not infected at that time, but in 1952, Zika was found in human blood samples from somebody from Tanzania.

"I think that was the first time it was isolated from a human being," Lutwama said.

After that, several samples containing the Zika virus were collected in Uganda, including Entebbe and Kisubi, but "since then no other samples from humans, mosquitoes or monkeys have been collected [in Uganda]," the virologist added.

Riddle of Ugandan immunity

The virus surfaced again around ten years ago when there was a large outbreak on the Pacific island of Yap in 2007. In November 2015, Brazil declared that Zika was a public health emergency after reporting births of babies with abnormally small heads.

But why has Africa, with the exception of Cape Verde, been spared the disease which has spread to at least 43 countries or territories, most of them in the Americas? Lutwama says that there are many viruses in Africa which are closely related to Zika.

"They probably confer some kind of immunity to the people here. This means that by the time the Zika virus comes in, a person already has some kind of immunity against it. Because of this immunity, when a person gets infected, there isn't a lot of growth of the virus in the person's body," he said.

Lutwama is now constantly travelling between Uganda, the US and Brazil, trying to establish how this immunity which protects Ugandans came into existence. He hopes that their antibodies will be help him find some means of stemming the epidemic raging in South America.