CARACAS, Venezuela (Reuters) - - Venezuela's President Nicolas Maduro said on Thursday that three people had died of complications linked to the mosquito-borne Zika virus and that suspected cases of Zika had risen to 5,221.

Brazil said on Thursday that three people who died last year had the Zika virus, although authorities could not confirm that Zika alone was responsible for their deaths.

Only one in five people infected with Zika experience illness and even then they are normally mild symptoms. The virus is still poorly understood by scientists and no proof yet exists to show it causes the birth deformations or any reported deaths.

"We have 319 confirmed cases, of which unfortunately 68 presented complications and we've had three deaths due to Zika nationally," Maduro said during a broadcast on state television.

He did not provide details of the deaths and did not mention the number of pregnant women thought to have the virus. The Health Ministry did not respond to earlier requests for information on the number of pregnant women with Zika.

Maduro said the number of suspected cases had risen to 5,221 in the period between Nov. 5 and Feb. 8. The only previous public estimate last month said there were around 4,700 suspected cases.

The World Health Organization has declared a global emergency over possible links to birth defects from the Zika virus, which has spread to more than 30 countries.

Doctors say Venezuela actually has a far greater incidence of Zika than publicly admitted and that the leftist government is not doing enough to combat the outbreak.

Chronic product shortages mean even pain killers and insect repellent are hard to come by.

Patients suffering Guillain Barre, an autoimmune syndrome that can cause paralysis and has been linked to Zika, are also struggling to find immunoglobulin for treatment.

Maduro on Thursday night thanked Brazil, China, Cuba, India, and Iran for helping provide medicines.

Doctors and non-governmental health organizations say they are monitoring dozens of pregnant women who think they might have suffered Zika during the first months of gestation.

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Epidemiologists say any potential cases of Zika-linked birth defects in babies would likely only come to light around April, given the virus is thought to have arrived in Venezuela in the last quarter of last year.

Scientists are investigating a potential link between infections of pregnant women and more than 4,000 suspected cases in Brazil of microcephaly, a condition marked by abnormally small head size that can result in developmental problems.

(Reporting by Deisy Buitrago and Alexandra Ulmer; Editing by Michael Perry)