The number of confirmed and suspected cases of microcephaly in Brazil associated with the Zika virus was down to 4,759 in the week through May 7, the Health Ministry said Wednesday, hundreds less than more than 5,200 suspected in late March.

As doctors and Brazilian health officials find that some suspected cases of microcephaly are not the disorder, the total number of confirmed cases in Brazil stands at 1,326. A further 3,433 cases are still being investigated.

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Brazil considers most of the cases of babies born with abnormally small heads since the start of a Zika outbreak last year to be related to the virus.

After heated debate among scientists following the initial scare over the outbreak, agencies including the World Health Organization and the U.S. Centers for Disease Control and Prevention have concluded that the virus can cause microcephaly in infants of mothers infected with Zika.

Most of the cases in Brazil remain focused in the country's northeast, where 1,190 cases have been confirmed. Though Zika infections continue to spread throughout Brazil and beyond, there has not been a concentrated surge in the number of microcephaly cases elsewhere.

In Brazil's southeast, which includes the major cities of Sao Paulo and Rio de Janeiro, 68 cases have been confirmed.