TO A curious thing happened when Hong Kong reopened schools after closing them due to the Covid-19 pandemic. It is worth looking here.
Hong Kong closed its schools to in-person learning from late January 2020 to late May, and then again in early July, when more cases of Covid were detected. Within weeks of the schools reopening in October, they began to see large numbers of children falling ill, despite the mandatory use of masks, the extra space between desks and other measures to reduce the risk of the spread of SARS- CoV-2, the virus. that causes Covid-19.
But the children were not infected with the virus. They also didn’t have the flu, which would have been another possibility. They were infected with rhinovirus, one of the most common causes of the common cold.
The researchers believe that the increase in illnesses was not an accident, but rather a consequence of the congregation of the children after so many months of social distancing. In short, they may have been more susceptible to respiratory viruses because they likely had fewer exposures to people outside their homes and therefore less chance of contracting them and developing immunity.
The findings were recently published in Emerging Infectious Diseases, the journal of the Centers for Disease Control and Prevention.
“I imagine places where schools have been closed for a long time are going to have the same experience as Hong Kong,” said Ben Cowling, professor of infectious disease epidemiology at the University of Hong Kong and lead author of the report. “That when the schools come back, suddenly there will be a lot of rhinovirus circulating, a lot of children will get colds, and then their parents will take it away and then they will panic because it could be Covid.”
A number of viruses that cause cold and flu-like illnesses have disappeared since Covid-19 began to spread around the world. There was virtually no flu activity during the southern hemisphere winter in July and August; So far this winter, only about 1,400 people in the United States have tested positive for influenza. By this time last year, more than 174,000 people had tested positive for the flu, a difference of more than 100 times. And at this time last year, 105 children had died of influenza in the country; this year, that tragic number has been reduced to just one child.
(Flu cases diagnosed by testing are the tip of the iceberg, even in a normal season.)
Also, infections caused by respiratory syncytial virus, or RSV, have decreased. RSV causes a cold-like illness that is usually mild; But in young children and older adults, the infection can be serious. In a typical year, about 58,000 children under the age of five are hospitalized with RSV and about 14,000 adults over the age of 65 die from it.
Rhinoviruses, on the other hand, mostly cause mild colds; The more than 200 viruses in the rhinovirus family are estimated to be responsible for about one-third of all colds. And, if the Hong Kong experience is any indication, it appears that they are not contained by the current measures to minimize the spread of Covid.
In total, there were 482 rhinovirus outbreaks reported by schools over a one-month period from late October to late November. The vast majority were in primary schools, kindergartens, nurseries and nurseries.
The population’s susceptibility to rhinoviruses and other respiratory viruses, including influenza viruses, may have increased over time because people were likely less exposed to the viruses when intense social distancing measures were implemented, including school dismissals, in response to the Covid-19 pandemic. ”Wrote the authors of the new article. “This would have increased the potential for transmission when schools were resumed.”
The authors, who are all from the University of Hong Kong, noted that British researchers had observed a similar phenomenon, reporting a sharp increase in rhinovirus infections in adults starting about two weeks after the children returned to school. in the UK last September.
Cowling and his colleagues had previously reported that the amounts of human coronaviruses and influenza viruses emitted by infected people are greatly reduced if they wear surgical masks, but this is not the case with rhinoviruses. That and the fact that rhinoviruses are resistant – they may be better able to withstand cleaning surfaces than coronaviruses and influenza viruses – may help explain why they continue to circulate while other respiratory viruses have decreased in incidence, they said. researchers.
Covid’s control measures likely don’t fully explain the phenomenon, said Ed Belongia, director of the Center for Clinical Epidemiology and Population Health at the Marshfield Clinic in Wisconsin.
Belongia noted that during the 2009 H1N1 flu pandemic, seasonal flu viruses and RSV practically disappeared for a time, although the use of masks was not common outside of some parts of Asia at the time and many of the distancing tools currently used were not part of the pandemic response.
“We really don’t understand what’s going on here in terms of these different patterns of virus circulation. Obviously, we don’t have a lot of experience with pandemics and what pandemics do to the circulation of other viruses, ”Belongia said.
The Hong Kong researchers noted that not only were there many cases of rhinovirus, but there were more serious infections than is normally seen, and some of the children required hospital care.
“It seemed to be more than usual,” Cowling said. “I think it has to do with that loss of immunity. Not only were many more susceptible children, perhaps they were more susceptible. “
The same phenomenon could occur with flu when flu viruses resume circulation, Cowling and others warn. Lack of exposure to flu viruses for more than a year could leave many people more susceptible to the viruses when Covid containment measures are eased.
“If I had to bet on it, I suppose we are likely to have a more severe epidemic next winter, assuming the restrictions are fully lifted by then,” John Edmunds, London School of Hygiene and Tropical Medicine and a member of the Sage committee of scientific advisers to the British government recently told the Daily Telegraph.
Cowling agreed. “Once the measures are relaxed, once people try to get back to normal, we will have the largest flu season ever recorded,” he predicted.