Researchers say that the Zika virus might be capable of doing more damage to fetal tissue than previously thought, Reuters reports.

The researchers studied the brain of a stillborn baby whose Brazilian mother was infected with Zika and found that the baby's brain was absent, a condition known as hydranencephaly.

Instead of tissue, the brain cavities of the baby were filled with fluid. The baby also had abnormal pools of fluid in other parts of its body.

The case was published in the journal PLOS Neglected Tropical Diseases.

The case was the first to link Zika virus with damage to fetal tissues outside the central nervous system.

So far, the birth defects associated with Zika virus have been linked to microcephaly, a condition in which babies are born with abnormally small heads. Although Zika has not been proven to cause microcephaly, scientists say the evidence that links the virus to microcephaly is growing stronger.

Brazil has confirmed more than 580 cases of microcephaly and is investigating more than 4,100 suspected cases.

The new study was led by Yale University tropical disease expert Dr. Albert Ko along with Dr. Antônio Raimundo de Almeida of Roberto Santos General Hospital in Salvador, Brazil.

"These findings raise concerns that the virus may cause severe damage to foetuses leading to stillbirths and may be associated with effects other than those seen in the central nervous system," said Dr Albert Ko, from the Yale School of Public Health (YSPH), according to Business Standard.

"Additional work is needed to understand if this is an isolated finding and to confirm whether Zika virus can actually cause hydrops fetalis," said Ko, who described the case with Dr Antonio Raimundo de Almeida from the Hospital Geral Roberto Santos in Brazil. 

On Feb. 1, the World Health Organization declared Zika a global health emergency.

Ko said the study's findings are hard to generalise because they are on just one case, but they are unusual.

Ko said the case suggests that the virus may be associated with stillbirths.

"We can't really prove there's a causal association, but it raises concerns," he said.

"Additional work is needed to understand if this is an isolated finding and to confirm whether Zika virus can actually cause hydrops fetalis," he said, in a press release.