LONDON — At least 12 people in southeastern England have died after an outbreak of a rare bacterial infection, the British health authorities said on Wednesday.

A total of 32 people in the county of Essex have been confirmed to have contracted the infection, invasive Group A streptococcal disease, National Health Service officials said in a statement. Most of those affected had been receiving care for chronic wounds either at home or in nursing homes. The average age of the affected patients was 87.

The risk of contracting the invasive infection “is very low for the vast majority of people, and treatment with antibiotics is very effective if started early,” Rachel Hearn, director of nursing and quality at the Mid Essex Clinical Commissioning Group, said in the N.H.S. statement. “We will continue to work with our partners in Public Health England to investigate how this outbreak occurred and take every possible step to ensure our local community is protected.”

The bacteria, which cause diseases like scarlet fever and strep throat, are often carried harmlessly on the skin, and spread easily between people through contact. Infections are usually mild, but they can turn life-threatening if they enter the bloodstream. Those with immune systems that are compromised by old age or illness are at particular risk.