Bulgaria's Foreign Ministry has advised the country's citizens to exercise caution when visiting parts of South America afflicted by mosquito-transmitted diseases.

The Brazilian Health Ministry has warned that there was "a very serious outbreak" of diseases caused by viruses carried by the Aedis Aegypti mosquito species, particularly Zika, dengue fever and a similar disease, chikungunya, the Foreign Ministry in Sofia said in a statement on Friday.

„Therefore, it is recommended that Bulgarian citizens traveling to or residing in Brazil, Colombia, Ecuador, Peru, Venezuela, Suriname and Guyana, exercised vigilance and caution and followed the instructions of the sanitary authorities,“ the statement read.

There have been 5,079 proven cases of Zika virus in Brazil since April 2015. Most cases were registered in Rio de Janeiro, 85, and there were 166 cases of microcephaly, the Foreign  Ministry said.Zika is suspected to lead to microcephaly, a condition in which infants are born with undersized brains and skulls.

It is believed that between 500,000 and 1.5 million Brazilians have been infected by Zika virus but only a few deaths from the disease have been reported.

The Zika outbreak in Brazil is the largest so far in the world, according to international health officials. The virus also has been found in other South American countries, including Colombia.