JAKARTA (Reuters) – More than 4,000 pigs have died after an outbreak of swine fever in the Indonesian province of North Sumatra, the head of the area’s food security and livestock agency said on Wednesday.

Carcasses have reportedly been found in rivers and on streets as owners discarded them out of fear of contagion, though the agency head M. Azhar Harahap stressed the virus is only infectious to pigs, not humans.

“The number of deaths is hovering around 4,000,” Harahap said by telephone.

Classical swine fever (CSF) virus, also known as hog cholera, was first detected in September in the province’s Dairi district, he said, noting the agency would open monitoring posts in 38 districts.

According to preliminary estimates by Indonesia’s statistic bureau, Indonesia produced 327,215 tonnes of pork meat last year, with the Hindu enclave of Bali producing the most. North Sumatra produced 43,308 tonnes last year.

Asia has seen a number of recent outbreaks of CSF virus and African swine fever, with the latter decimating China’s pig herd, the world’s biggest.

A year-long pig epidemic has slashed China’s pig herd by more than 40%, and has pushed prices of the country’s favorite meat to record levels.

(Reporting by Jessica Damiana; Writing by Stanley Widianto; Editing by Louise Heavens)