Czech health officials on Thursday announced the first cases of the mosquito-borne Zika virus in the Czech Republic, saying they would provide further details at a press conference later in the morning.

The World Health Organization declared the Zika outbreak linked to thousands of birth defects in Brazil an international health emergency on Feb. 1, citing a "strongly suspected" relationship between Zika infection in pregnancy and microcephaly in newborns.

It was not clear where the people in the Czech Republic contracted the virus or whether they had traveled to countries such as Brazil, where Zika has hit hardest.