At least four babies have been born in New York City with Zika-related brain developmental symptoms since July, the city’s health department said on Wednesday, bringing the total number of such births to five.

The numbers were announced in an alert the Department of Health and Mental Hygiene sent to doctors, urging them to remain vigilant and to continue to warn pregnant women and sexually active women of reproductive age not using a reliable form of birth control against traveling to places where the virus is spreading.

It was a reminder that while the threat of the virus may have eased in many places around the world, it still poses a danger and its consequences are likely to be felt for some time.