An army of mosquitoes will be infected with bacteria and released into Brazil and Columbia to combat the Zika outbreak.

Scientists are hoping that the millions of modified insects will mate with the local insects and spread the Wolbachia bug throughout wild populations.

Although the Wolbachia bacteria is harmless to humans, it stops mosquitoes transmitting Zika virus.

Zika has spread through 50 countries in the past year and is believed to be responsible for nearly 2,200 cases of microcephaly – where babies are born with shrunken heads and brain damage.