The magnitude of the Omicron wave is beyond the authorities responsible for quantifying it. The virus is spreading so quickly that even attempts to trace contact cases are falling into disuse.
The World Health Organization estimates that the pandemic is “under control” when the positive rate of laboratory tests is below 5%. The rate of 24.9% established Sunday in Quebec – an absolute record – “shows that we do not have quite the control over our epidemic and that we underestimate the cases”, confirms the DD Judith Fafard, medical director of the Laboratoire de santé publique du Québec.
Just like the DD Fafard, professor at the School of Public Health of the University of Montreal Roxane Borgès Da Silva cannot estimate the actual contamination data. A simple observation around you can see the difference between the number of PCR tests carried out and the number of positive cases detected only by a rapid test, she notes. “We have seen so many people who have canceled parties because they had symptomatic people in them and positive for antigen tests. This means that the number of cases we currently have is not representative of what we have in the population. “
The positivity rate is also very high since the government only invites symptomatic people to be tested.
Even the hospitalization curve, a “late” but rigorous indicator, does not make it possible to estimate with precision the extent of the current surge in contamination. Preliminary studies indicate that the hospitalization rate for the Omicron variant is lower than with previous variants, confusing comparisons, says DD Fafard. “It may be that this indicator of hospitalization cannot be compared with that of Delta or Alpha. “
“When we will see the positivity rate go down, it will still give us an idea of the circulation of the virus in the community,” she qualifies.
The real number of cases of contamination may thus remain forever unknown. However, there is a scientific method to prove that we have been infected once the disease is behind us. ” It can be done. Certain serologies allow us to differentiate between immunity acquired by vaccination and immunity acquired by infection, ”explains Judith Fafard. However, this analysis a posteriori cannot determine if the contamination occurred during the Omicron wave or during a previous wave. “I would be surprised if it was offered to everyone”, adds the DD Fafard.
Tracing now obsolete
Not only is this number of actual cases higher than what is announced daily, but the authorities are also overwhelmed in their quest to trace all contact cases.
The fault lies with Omicron’s very short incubation period which is between a day and a half and three days in most cases. “The time to have the declaration of the case, to reach the person, to ask questions about his contacts, there has already been a second generation which has had time to transmit the virus to a third generation,” explains DD Fafard. Contact tracing with Omicron, I don’t want to put people off, but it might not pay off much. “
The responsibility now falls on individuals to curb transmission, notes Mathieu Maheu-Giroux, epidemiologist at McGill University. “If people use rapid tests and call their contacts so positive themselves, that’s tracing. And it can help reduce transmission. “
The screening capacity of the Quebec state peaks at around 45,000 tests per day, due to laboratory equipment, which cannot provide more results. “It’s like your microwave is running 24 hours a day. At some point, it’s going to be faulty. There is a limit to pushing these machines, ”explains DD Fafard.
Public Health is currently working on an online “self-report” platform to identify all positive cases that will not be tested in the laboratory.