India is on high alert after a resurgence of the potentially deadly Nipah virus (NiV), which has killed at least two people in recent days and sparked the testing of hundreds more in southern Kerala state.

It’s the third time in five years that the brain-damaging virus, which can spread from bats and pigs to humans, has surfaced in the Kozhikode district of Kerala. In a 2018 outbreak, 21 people died before it was contained. The virus has previously been detected in countries including Singapore and Malaysia. Here’s what you need to know about it:

Bloomberg