How common is the British variant (B.1.1.7) in Portugal? It is estimated that this variant already accounts for 42% of cases across the country and around 60% in Lisbon.
The spread of this variant in the country has the contribution of a real-time tool developed in collaboration between the National Health Institute Doutor Ricardo Jorge (Insa) and Unilabs – Portugal (a laboratory for clinical analysis). To determine the prevalence, a calculation is made between virus samples assigned to the variant within a set of positive SARS-CoV-2 samples collected by Unilabs. This number is then extrapolated to all positive cases in the country.
Last week (on January 29), João Paulo Gomes (researcher at Insa) said at a joint hearing with other experts from the Commission for Monitoring the Application of Response Measures to Pandemics and Economic and Social Recovery in Parliament variant was in “exponential.” Growth “in Portugal”. At that time it was estimated that between 35% and 40% of the total cases of Covid-19 in Portugal were already caused by the variant. B.1.1.7 is between 40 and 70% more transmissible than other circulating ones Variants and has already been proven in more than 70 countries.
According to this week’s data at the global level, the prevalence is estimated to be already 42% of the national total, according to a source from the process notified to the PUBLIC this Friday. In particular, the values by district (where the number of samples is greater), in Braga the prevalence is 19%, in Porto 28%, in Coimbra 48%, in Lisbon 58.4% and in Setúbal 52%. Therefore, in other counties of the country where the number of samples is small – according to the same source – the national total, which is 42%, should be considered, rather than just the percentage of counties with few samples.
The development of the tool that leads to the determination of prevalence was possible because, through genomic sequencing, there is a strong correlation between failure to detect a coronavirus gene and the presence of the variant. How did it happen? Many laboratories use a diagnostic test that detects the virus through three parts of SARS-CoV-2 at the same time, and one of them is the S gene. It turned out that there was a large percentage of samples that failed to test this gene, which is indicative of the existence of the variant – which led to the development of the tool.
An article published on the virology website that used this tool identified the prevalence of the variant in data analyzed up to January 20. With these data and the infection dynamics at the time, it was found that the relative frequency of the variant increased at a rate of 70% per week. Therefore, it was predicted that the variant could account for around 60% of cases of Covid-19 in Portugal by the first week of February (this week that we are in).
Last week, João Paulo Gomes stated on the Contingency Committee that the weekly growth rate was estimated at 90%. “We also estimate that within three weeks around 65% of all Covid-19 cases in Portugal are caused by the British variant,” he said.
But if this week the variant was expected to account for 60% of the cases in the country and the value is estimated to be less – 42% – has the spread of the variant in the country slowed? If so, is this already due to the containment measures?
Elisabete Ramos (professor at the University of Porto Medical School) says she doesn’t know the methodology used to get these numbers and doesn’t know the reason for the difference. Basically, he says that there can be different hypotheses: the situation is improving and there can be a slower development of the variant; The original model may have been less accurate. or the source of the samples may have varied in different places, lists the President of the Portuguese Association for Epidemiology.
Paulo Santos, researcher at Cintesis (Center for Research in Health Technologies and Services), emphasizes that these are estimates: “We have to be careful with predictive models because they never take into account all variables.” Carla Nunes emphasizes that the weight of the Variant could have decreased proportionally, that is, it has lost its importance in transmission, although there are more cases. “The new variants [com características mais preocupantes] They always bring new challenges with them, “says the director of the National School of Public Health at Universidade Nova de Lisboa, adding that the measures, including the restriction, are already being applied effectively in B.1.1 for other variants of the virus. 7th