Story highlights Previously, the WHO said there was not yet enough scientific evidence to say the virus caused these conditions

More than 1,000 cases of microcephaly linked to Zika have been reported in 6 countries

Nearly 400 cases of Zika-related Guillain-Barre have been reported in 13 countries

(CNN) The World Health Organization says the mosquito-borne Zika virus causes microcephaly and Guillain-Barre syndrome.

"Based on a growing body of preliminary research, there is scientific consensus that Zika virus is a cause of microcephaly and Guillain-Barre syndrome," the World Health Organization said in its weekly Zika virus situation report Thursday

Previously, the agency said there was not yet enough scientific evidence to say the virus caused these conditions, although it was likely.

More than 1,000 cases of microcephaly and other fetal malformations believed to be Zika-associated have been reported from six countries, according to the WHO.

There have been nearly 400 cases of Guillain-Barre syndrome in patients with confirmed or suspected Zika virus infection in 13 countries.