Experts have ruled on what caused 12 monkeys at the same zoo to die last month – and it’s a disease which can affect humans.

Of the dead monkeys at Hong Kong’s Zoological and Botanical Gardens, 11 confirmed succumbed to melioidosis, a bacterial infection. It likely stemmed from contaminated soil disturbed during digging work in the gardens last month, according to Hong Kong Free Press.

Melioidosis is a bacterial infection in people and animals. Melioidosis is spread through contact with contaminated soil, air, or water. Cases may increase after hurricanes, heavy rain, and other severe weather events, according to the CDC. The disease is often confused for other conditions, making diagnosis difficult.

A health officer assured the public the incident is “an isolated infection that happened in an individual zoo. We believe it will have a small impact on residents and people should not be overly worried.”

Parts of the zoo were sealed off and disinfected and experts were called in to conduct necropsies and toxicological tests after the incident late last month.

Nine of the monkeys died across just two days after displaying unusual behaviour at Hong Kong Zoological and Botanical Gardens.

A 2004 study into the effects the condition has on animals found that dogs with the disease were shown to have “fever, aggressive behaviour, rapid, panting respiration and continuous profuse salivation”.

Symptoms in humans include fever, cough, chest pain, headache, respiratory distress, abdominal or chest discomfort, disorientation, seizure, loss of appetite, sores, ulcers, or abscesses, swollen lymph nodes, and weight loss.