Zika-Linked Cases of Microcephaly Rise in Brazil

The number of cases of microcephaly in Brazil associated with the Zika virus has risen to 4,863—up from 4,690 a week ago.

Confirmed cases of the virus reached 641, while suspected cases now total 4,222, Reuters reported on Wednesday morning, citing the Ministry of Health.

The Zika epidemic—which is now spreading through the Americas and prompting a dedicated response from the U.S. Centers for Disease Control and Prevention—is centered in Brazil.

Read more: How Brazil Uncovered the Possible Connection Between Zika and Microcephaly

Doctors believe the virus is linked to microcephaly, a birth defect involving an abnormally small head and incomplete brain development, though there is not yet definitive scientific proof of the link.

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Write to Katie Reilly at Katie.Reilly@time.com.