Canada is experiencing a record number of cases of dangerous and rapidly progressing streptococcal infections.
Invasive group A streptococcus, or iGAS, is a bacterial infection that can cause serious, life-threatening complications. Provinces have also reported dozens of deaths in recent months alone, including at least 10 children in Ontario and British Columbia.
The latest tally of 4,600 iGAS samples processed for 2023 suggests the infection rate could now reach 12 cases per 100,000 people.
Here’s a look at common symptoms, when to see a doctor, and who is most at risk.
What is invasive Strep A?
Group A streptococcus is a family of bacteria that causes mild illnesses, such as strep throat or skin infections.
John McCormick, professor of microbiology and immunology at the University of Western Ontario, explains that there are non-sterile sites in our bodies where bacteria can exist without major concern.
In rare cases, the bacteria may travel to a sterile site, such as blood, soft tissue, or under the skin. This is when the most dangerous invasive infection occurs. Group A streptococcal bacteria in these locations can lead to toxic shock syndrome, necrotizing fasciitis (flesh-eating disease), meningitis (inflammation around the brain), and sepsis (a blood-borne infection).
How do you know if you have it?
Both forms of group A strep infection share symptoms such as redness, pain, and fever. But a person with invasive group A streptococcus will be very, very sick, according to Dr. Donald Vinh, an infectious disease specialist at the McGill University Health Center in Montreal.
“What we know is that when people come to the hospital and have GAS, they tend to be very sick,” Vinh said. “Typically, if you’re well or, you know, well enough to go about your normal activities, you generally don’t have iGAS.”
Watch for symptoms such as lack of mental awareness, difficulty breathing or chest pain, nausea, dizziness and low blood pressure, he said.
Acetaminophen is normally effective in lowering a fever caused by a group A strep infection. “If it’s not, that’s a worrying sign,” said Dr. Brian Conway, medical director of Vancouver Infectious Disease Center.
Since iGAS can cause many different complications, people should also be on the lookout for symptoms of necrotizing fasciitis, meningitis, and sepsis.
Necrotizing fasciitis can cause extreme pain and redness that spreads quickly to specific locations on the body. Symptoms of meningitis include severe headache, neck stiffness, vomiting, sensitivity to light, and confusion. Sepsis can cause fever or low body temperature, difficulty breathing, clammy or clammy skin, and extreme pain.
Experiencing any of these symptoms is reason to see a doctor, Vinh said.
If in doubt, most provinces have an 811 health information line, which will connect you with a registered nurse, Conway said. These telephone lines are in service 24 hours a day.
How can I get tested?
Having strep throat doesn’t mean you’ll definitely develop iGAS — and you can develop iGAS without having had strep throat, Vinh said.
“It’s not on a continuous spectrum. We think they’re different syndromes caused by the same bacteria.”
Nonetheless, you should still get tested and treated for strep throat, Vinh said, because complications could arise. Rapid strep tests can be done at many doctor’s offices and even some pharmacies.
McCormick also said people should get checked for strep throat, noting that an invasive infection can move quickly.
But, he added, “it’s a rare type of thing, so the general population shouldn’t be very worried.”
There is no publicly available test to diagnose iGAS.
It is diagnosed by finding group A streptococcus in a body sample where bacteria would not normally be found, Vinh said.
“For example, it will take samples of your blood or samples of fluid around your lungs,” he said. These tests should be done in a hospital.
How is it treated?
An iGAS infection is treated with high doses of intravenous antibiotics.
If serious complications occur, such as sepsis or necrotizing fasciitis, surgery and amputation may be necessary.
Conway said cases of severe sepsis would require a patient to be admitted to the ICU. “There may be damaged organs, like your kidneys, that may not be completely reversible.”
Who is at risk?
One study found that the flu or chickenpox precedes iGAS in about 15% of cases.
“Previous viral infections can predispose people to invasive disease,” McCormick said, “the most serious one is actually chickenpox.”
He said children who develop chickenpox, which is a viral infection, are much more likely to develop streptococcal disease. This is because chickenpox creates skin lesions, which then create portals for bacteria to enter.
Conway said anyone with a weakened immune system, “especially if they have underlying heart or lung disease,” is at risk.
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There is currently no vaccine for Strep A, but it is recommended to get vaccinated against flu, COVID-19 and varicella (chickenpox), Vinh said.
“If we prevent this event in advance, we believe we will subsequently prevent or reduce the risk of invasive group A streptococcus.”