National Institute of Allergy and Infectious Diseases via AP This handout image provided by the National Institute of Allergy and Infectious Diseases shows an electron microscope image of group A streptococcus (orange) during phagocytic interaction with a human neutrophil (blue).

Of the cases, 22 per cent required treatment in intensive care, 15 per cent had Streptococcal Toxic Shock Syndrome and 15 per cent had necrotizing fasciitis — also called "flesh-eating" disease.

The outbreak was declared more than 18 months ago and the Middlesex-London Health Unit says more than 132 cases of infection have been reported since April 1, 2016.

LONDON, Ont. — Health officials have issued an alert, saying nine people have died in an ongoing invasive group A streptococcus outbreak in the London, Ont., area.

Associate Medical Officer of Health Dr. Gayane Hovhannisyan says about half of the cases have been among injection drug users and/or people without access to stable housing.

Symptoms depend on the site of the infection and may include fever, chills, sore throat, dizziness, confusion, severe pain, redness or swelling around a wound or injured area.

We need a better understanding of what's happening.Dr. Gayane Hovhannisyan

Hovhannisyan says the alert has been issued because the health unit is seeing an increase in infections among people who have no connection to the outbreak in people who inject drugs or don't have stable housing.

"We need a better understanding of what's happening, which is why we've issued this alert," she said Monday in a news release.

Infections increase in winter

The bacteria are spread by direct contact with nose and throat secretions from an infected person, or by direct contact with infected wounds or sores on the skin.

While the infections can occur year-round, the health unit said Monday that the number of infections tends to increase during the winter.

It said the majority of streptococcus infections cause relatively mild illnesses like strep throat, but sometimes more serious and potentially life-threatening infections are able to get into muscles, blood and other organs.

The health unit advises regular handwashing, covering the mouth and nose when coughing or sneezing, avoid sharing drinking and eating utensils and to not share drug paraphernalia in an effort to avoid infection.

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