Viral respiratory infections follow a predictable pattern, peak in January: U of A research

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Viral respiratory infections in Alberta follow a predictable pattern and are much worse every two years, a study of more than 37,000 cases over 10 years found.

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The researchers say the predictable ebb and flow could help the healthcare system plan ahead for waves of sick patients, while warning that January 2022 will be the peak of a bad season for cases.

The team, led by lead researcher Dr. Michael Hawkes, a professor of pediatrics at the University of Alberta, analyzed six different respiratory viruses with a central focus on respiratory syncytial virus (RSV), a virus that often causes hospitalizations in babies.

In an interview Friday, Hawkes said most doctors know anecdotally that respiratory virus cases peak in the winter and are much lower in the summer. The formal investigation confirmed that the number of cases peaks in January and bottoms out in June. It also detected a pattern of a bad year with a high number of cases followed by a good year.

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“It wasn’t the kind of thing you said, ‘Oh, that’s just a random occurrence.’ It was with such clock-like regularity that we thought there must be something underlying this, ”he said.

In the case of RSV, Hawkes said a year of high case counts translates to 200 cases per week in January compared to half the following year. In a bad year, 80 babies come to the hospital per week, compared to 40 in a good year.

Hawkes suggests that the pattern could be explained by decreased immunity to the viruses they studied over a period of one year.

“A strong and bad year for viruses will be followed next year with a high percentage of immune (people) in the population, so the virus may not take off as well in the next season,” he said.

“On the other hand, in a good year, a year of low infection, there will not be as many immune systems in the following winter and therefore the virus can take off.”

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Being aware of the predictable pattern means hospitals can know what’s coming and prepare, he said.

In the case of RSV, babies at higher risk may receive preventive antibody treatment, he said.

“We need to plan the resources for these winter waves of hospitalizations. In January, many of our wards are full of babies with RSV, so it is necessary to plan the number of beds and the nursing staff to adapt to that, ”he said.

Hawkes said the pattern shows that the coming December and January are going to see a high number of cases.

“Because in COVID nobody came out, nobody got RSV. It was an extremely low year… there were hardly any RSV hospitalizations last year, ”he said.

The research itself did not specifically look for COVID-19, but four of the viruses that were studied are similar. That could mean that COVID-19 would follow a similar pattern, but Hawkes said the virus is too new and affected by restrictions to know for sure.

“We are really altering their pattern, their natural pattern, with vaccination, with confinements, with masks and social isolation. Then those things will alter the natural patterns that we have observed here, ”he said.

“So it’s a bit difficult to predict, but it’s good to know what would happen in a natural situation with COVID-19.”

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