As reported in The Guardian:
More than 350 elephants have died in northern Botswana in a mysterious mass die-off described by scientists as a “conservation disaster”.
A cluster of elephant deaths was first reported in the Okavango Delta in early May, with 169 individuals dead by the end of the month. By mid June, the number had more than doubled, with 70% of the deaths clustered around waterholes...
The Botswana government has not yet tested samples so there is no information on what is causing the deaths or whether they could pose a risk to human health. The two main possibilities are poisoning or an unknown pathogen. Anthrax – initially considered the most likely cause – has been ruled out.More at the link.