Health warnings have been issued in London following an outbreak of toxic caterpillars. Hairs on the Oak processionary moth caterpillars, or OPM caterpillars, can cause fevers as well as eye and throat irritation. They can be deadly for those with asthma. According to the Telegraph:

Serious allergic reactions can be caused by protein in the creatures’ hair follicles, which remain active on the ground for up to five years after being shed…Each OPM caterpillar has about 62,000 hairs which can be ejected…The hairs also remain in the oak tree nests, which start out white but become gradually discoloured and harder to see.

The species is believed to have to have arrived in Britain accidentally in 2005 via Dutch trees imported for a landscaping project at a housing development in Kew, South West London.

Health officials warn that people should not “touch or approach nests or caterpillars” or let children or animals near them.