It is the first time that Spain has recorded cases of monkeypox, a disease native to West Africa with characteristics similar to chickenpox and secondary syphilis. It is spread through fluids and its initial symptoms are similar to those of common smallpox, although milder. They include pustules, fever, headache, muscle aches, back pain, swollen lymph nodes, chills, and exhaustion.

Infected animals, usually rodents, transmit it to humans through bites or their droppings. Between humans, contagions are produced by fluids, saliva, respiratory excretions, by contact with the exudate of the lesion or the material of the scab or also by faeces mixed with food, for example.