The bacterium is usually found living harmlessly on the skin, nose or throat
Infection control procedures at an Edinburgh hospital have been "reinforced" after a woman died from a Group A streptococcal infection.
The 86-year-old patient died in Liberton Hospital on Saturday.
The group A infection is caused by a bacterium usually found living harmlessly on the skin, nose or throat. The ward is not accepting new patients.
An elderly man, who had been an inpatient in the same hospital, is also seriously ill with the infection.
He is currently being treated at the ERI.
Another elderly patient is currently undergoing tests and treatment at Edinburgh Royal Infirmary after he showed symptoms similar to the infection.
NHS Lothian said as a precaution, it had reinforced infection control procedures in Liberton Hospital to help protect patients, staff and visitors.
Tests are also underway to establish the source and strains of the infection.
Dr Alison McCallum, NHS Lothian director of public health and health policy, said: "Our thoughts are with the families at this time.
"Fortunately, in the vast majority of group A strep cases, patients will only suffer mild symptoms and make a full recovery.
"However, group A strep can be serious for elderly people and others with underlying health conditions.
"We have reinforced infection control measures in place to protect patients, staff and visitors."
The infection can result in a sore throat or skin infection such as impetigo and can also cause respiratory infections.
There are about one to four serious cases per 100,000 population in Scotland.