Nearly 1,000 seals and sea lions in southern Brazil have died from bird flu, according to authorities, who are trying to isolate the deadly virus to prevent it from spreading to poultry farms.

The country’s southernmost state of Rio Grande do Sul has confirmed an unprecedented 942 deaths of these marine mammals after contracting highly pathogenic avian influenza (HPAI), which was first detected in the South American country this year.

Oceanographer Silvina Bota of the Federal University of Rio Grande (FURG) said animal carcasses should be buried or cremated as soon as possible to reduce the risk of contamination to humans or other animals.

Scientists also found some marine mammals that had convulsions along local beaches as the virus attacks their nervous systems. Under government health regulations, these animals must be euthanized to spare them “a very painful death,” according to Botha.

After Brazil’s first case of HPAI in wild birds in May, the Ministry of Agriculture announced that preventive measures taken had prevented an outbreak of the virus on commercial poultry farms, which could have triggered export bans against Brazil, which is the world’s largest exporter of chicken.

However, the virus escaped control in other animal populations. In addition to the outbreaks among seabirds, seals and sea lions, authorities have collected samples for testing from dead seals and penguins found on shore, but there are no confirmed results from the analyzes being carried out yet.

Botha explained that the first diagnosis of HPAI-related marine mammal deaths in the Rio Grande do Sul occurred in September, when unusually high mortality rates attracted the attention of scientists. Three cities in that state still have active outbreaks.

The spread among marine mammals appears to have started in Peru, and then the virus spread to South America, affecting wildlife in Chile, Argentina, Uruguay and now Brazil, according to the scientist.

Brazil’s agriculture ministry reported 148 outbreaks of HPAI in the country, mostly along the coast, declaring a public health emergency to contain the disease, which it noted is “not yet considered endemic in Brazil.”

Bird flu has led to the killing of hundreds of millions of farmed animals in Europe and the US.