Delta variant
First detected in India, this is considered a “concern variant” by the World Health Organization (WHO) as it has been shown to increase transmissibility, cause more serious illness and reduce the benefit of vaccines and treatments.
Its high transmissibility – considered Delta's “superpower” by Shane Crotty, a virologist at the La Jolla Institute of Immunology, in San Diego (USA) – gives the immune system less time to respond and mount a defense. Whereas in the original mutation, the coronavirus takes seven days to cause symptoms, in the Delta strain it is two or three days faster.
In addition, this variant also seems to be undergoing a greater mutation, with the emergence of reports of a “Delta Plus” variant, detected, according to Outbreak.info – Covid-19 open source database -, in at least minus 32 countries. It is still unclear whether it is more dangerous, hence it is not yet considered a variant of concern by the WHO.
Lambda variant
This strain, first identified in December in Peru, is now classified as a “variant of interest” by the WHO, meaning it may cause a change in transmissibility or a more serious disease, but is still under investigation.
Lambda has shown a decline in transmissibility, with the percentage of new cases decreasing, according to GISAID – database that tracks the SARS-CoV-2 variants. In addition, William Schaffner, a specialist in infectious diseases, says that vaccines are well resisting this variant, although carrying mutations that can be resistant.
According to the INSA report, no new cases of this variant were detected, with a strong circulation in the regions of Peru and Chile.
B.1.621
Considered “variant of interest” by the European Center for Disease Control and Prevention, B.1.621 first appeared in Colombia in January and carries several key mutations, including E484K, N501Y and D614G, linked to increased transmissibility and the reduction of immune protection.
It also has a low frequency in Portugal, with a detection rate below 0.8% since week 25 (21st to 27th June), according to the INSA.