In the face of a real viral infection it may mean that the attention of the immune system is diverted letting a bacterial infection in.

BBC: 'Wrong' immune response aids TB

It can carry Lyme disease, a bacterial infection which can attack the skin, heart and nervous system.

BBC: NEWS | UK | Magazine | Itching to get at you

Bacterial vaccines, which used modified bacteria to try to train the immune system to fight the HIV virus.

FORBES: HIV Vaccines: The Shotgun Approach

As with many illnesses, vulnerability to flesh-eating bacterial infections increases with age and underlying conditions that might compromise the immune system.

CNN: Surviving a flesh-eating disease