New York: A team of US researchers has documented for the first time the disease trajectory of Zika virus that started with nine positive patients and has now spread to more than 13,000 infected individuals in Colombia.

In October last year, a team at University of Wisconsin-Madison (UW-Madison) and Universidad de Sucre in Colombia ran the first tests confirming the presence of Zika virus transmission in the South American country.

“Colombia is now only second to Brazil in the number of known Zika infections,” said study lead author Matthew Aliota, research scientist in the UW-Madison School of Veterinary Medicine (SVM).

His research on Zika virus shows that the virus has split into two distinct lineages — African and Asian. The Colombia strain of the virus can be tracked to Brazil, which can be traced to a strain that originated in French Polynesia.

“There is certainly something different about these viruses that have allowed or facilitated this geographic expansion,” Aliota added in a paper published in the journal Emerging Infectious Diseases.

Zika virus, which spreads among humans via mosquitoes, causes illness characterised like many other viral infections by fever, rash and joint pain.

Officials estimate that four out of five people who contract the virus do not get sick and the virus is rarely fatal.

However, pregnant women in Brazil infected with Zika have given birth to babies with small heads and underdeveloped brains, a condition called microcephaly.

“If you are pregnant or planning on being pregnant, absolutely, cancel your vacation,” Aliota added, echoing the US Centers for Disease Control and Prevention warning that pregnant women not travel to the more than 20 countries now known to have active Zika transmission, like Brazil, Colombia, Ecuador and in the Caribbean.

In these countries, mosquitoes are spreading the virus to people.

The symptoms of Zika virus are “really nonspecific and it overlaps with a lot of things, especially with dengue virus and chikungunya”, Aliota noted.

“It’s hard when someone comes in with a fever and a rash to narrow it down,” he added.

Zika virus was first found in Uganda in 1947 but remained limited to Africa and Southeast Asia for decades. But in 2007, an outbreak occurred in the Pacific Islands and recently the virus began to spread in the Western Hemisphere.

The team is now looking for ways to control it. As members of the “Eliminate Dengue” programme, an international effort managed by Monash University in Melbourne, Australia, they have explored how a bacterium that infects 60 percent of insects around the world may be used as a tool to combat the spread of dengue and similar mosquito-borne viruses.

Zika, dengue and chikungunya (which are also found in Colombia) are RNA viruses, which refers to how they encode their genetic material, and each is transmitted by a specific mosquito called Aedes aegypti.