Infectious disease experts say having a virus like the common cold could keep others away, as each germ essentially rotates between fall and winter. Respiratory syncytial virus, or RSV, infections are stabilizing across the country and the flu is on the rise, according to Public Health Canada. Canadians are mingling and traveling freely again. Mixing people together gives scientists a rare opportunity to watch how the different respiratory pathogens we carry interact after a pandemic. Until now, most research on viruses has focused on a single pathogen at a time, either in a single patient or in an entire population. Here’s a look at the early science about why we probably won’t see multiple viruses hitting adults at once—and who might be most vulnerable to a double or triple strike. Multiple viruses may not strike adults at the same time, but children may face a double whammy or worse. Scientists are investigating how and when viruses interfere with each other. (BSIP/UIG/Getty)
The virus activates the immune defense
Although the idea of viruses interfering with each other has been discussed since the 1960s, the 2009 H1N1 flu pandemic gave scientists some further clues about it. Dr. Guy Boivin, a virologist and professor of pediatrics at Laval University in Quebec City, wrote a comment earlier this year looking at the evidence on viral interference — competition between respiratory viruses that interfere with or block each other’s spread. “It was remarkable that the [H1N1 flu] The pandemic virus appeared in France two to three months after it appeared in other European countries,” said Boivin. “This was related to a rhinovirus outbreak at the time. This small rhinovirus outbreak delayed the H1N1 pandemic in France.” Rhinovirus is a type of the common cold virus. As for the waves of different respiratory infections such as COVID, RSV and influenza circulating in Canada, Boivin said he expects some overlap. But he also believes it’s unlikely to all peak at once, because catching a bug can offer short-term protection against other viruses. WATCHES | Updated respiratory virus precautions:
What would it take to wear masks again? | For this
Health experts in Canada and the US are recommending that people start wearing masks again with a “perfect storm” of respiratory illnesses on the rise, a strain on our hospital systems and drug shortages. But is that enough to make us wear masks again? Dr. Susy Hota joins About That with Andrew Chang to walk us through it all. Dr. Helen Foxman, an immunologist at the Yale School of Medicine in New Haven, Conn., studies antiviral defenses in her lab, including how viral interference it happens. “Having a virus activates the antiviral defenses in your body,” Foxman said. “This may also protect against other viruses, at least for a short time.” Foxman said it’s possible that having one infection makes you less likely to get another at the same time. For example, if human airway tissues are infected with rhinovirus and then H1N1 influenza is introduced a few days later, the influenza virus will not grow. “It was because the defenses that the tissue activated in response to the rhinovirus also protected against the flu,” Foxman said. She is currently looking at interference between the virus that causes COVID-19 and other viruses in human airway samples in her lab. A view of the Bichat hospital where the French health ministry said a patient was being treated for a confirmed case of pandemic H1N1 flu in May 2009. Scientists say another virus appeared to suppress H1N1 initially in France. (Benoit Tessier/Reuters)
Short term protection
Foxman said the lining of our airways goes into an antiviral defensive state when they sense an intruder. The protective defense is one of the immune system’s many layers of protection. One is called interferon: a family of proteins produced by the body’s immune system in response to an invading viral infection. As the name suggests, interferon interferes with or blocks the ability of a virus to achieve its raison d’être of making copies of itself. Instead, interferon summons immune cells to the site of invasion so they can take up arms against the threat. But interferon doesn’t stay activated for long, cautioned Dr. Alison McGuire, an infectious disease specialist at Sinai Health System in Toronto. “It’s not an effect with most viruses, and it’s not a big effect,” McGeer said. Dr. Allison McGeer, an infectious disease specialist at Sinai Health System in Toronto, says the effect of viral intervention is small. (Evan Mitsui/CBC) The opposite can also happen. Some people get double or co-infections — two or more bugs at the same time. Why this happens is not well understood, and the extent to which this happens is only just beginning to happen explored. McGeer said co-infections occur “not infrequently” among children admitted to the hospital.
Multiple infections of the baby at the same time
Emilie Doré’s six-week-old son, Diego, was one of them. “My mother’s instinct was telling me it was a bad cold in a baby who is very small, very small,” Dore recalls. Baby Diego was hospitalized at Montreal Children’s Hospital for four days with multiple respiratory infections. (Submitted by Emilie Doré) Dore was on the lookout for symptoms in the infant after her two-year-old daughter fell ill. First the baby had a little congestion and a cough followed by lethargy and fever. “I would say the most upsetting and worrying moment was when he had to be put on oxygen because he was having trouble breathing,” said Montreal’s mother. When he wasn’t getting better, Diego had a lumbar puncture or spinal surgery. Tests showed he had RSV, rhinovirus and enterovirus, another common cold virus, as well as possibly meningitis. She recovered after four days in hospital and is now eight weeks old. Baby Diego has now recovered. (Submitted by Emilie Dore) Virologists say that at the population level, other factors such as human behavior of different age groups, population immunity, environmental conditions such as temperature and humidity, and what happened during the COVID-19 pandemic also affect triple threat of virus spread. Separate waves of each virus may continue to sicken people and increase demand on emergency departments and primary care services at a time when they are struggling with staff shortages and delays. Dr Gerald Evans, chair of infectious diseases at Queen’s University and Kingston Health Sciences Centre, said that when people in hospital are tested for respiratory infections now, three viruses can be present. “We’re starting to get a little bit of a message that people can get both flu and COVID, and certainly in children we’re seeing flu and RSV showing up,” Evans said. “So the impact of that co-infection we still have to figure out. We’re seeing that. It’s small numbers.”
