New SARS-CoV-2 Variant in Mexico: The Emergence and Spread of BW.1

A new Covid-19 variant has been identified in Mexico, which could be the cause of a new coronavirus outbreak: BW.1, commonly known as Xibalbá, the Mayan underworld. According to the analysis, said sublineage predominates in the southeast of the country.

The current variant of the SARS-CoV-2 virus, predominant in the southeast and center, may have emerged in July 2022 in the Yucatan Peninsula. Popularly known as Xibalbá, it is officially called BW.1 and is a descendant of omicron, which spread to the United States and other regions of the world, according to a study conducted by specialists from UNAM's Institute of Biotechnology (IBt), Rodrigo García López and Alejandro Sánchez Flores.

"The early identification of this new variant that is being seen in Mexico allows us, for the first time in the history of the pandemic, to have information that will help us apply effective measures to prevent and not only describe what happens in a wave (of contagions)," emphasized Sánchez Flores.

The Mexican Genomic Surveillance Consortium, to which the IBt belongs, has been monitoring the cases in the Mexican Republic and called their attention to the fact that since last October there has been a considerable increase in the Yucatan Peninsula. As part of the surveillance, the genomes of those samples positive for SARS-CoV-2 are sequenced.

"Upon review, we saw a large proportion of a variant that was identified as BW.1, which was genetically very similar to one that had been circulating in July of this year, which is BA 5.6.2, so we began to analyze which mutations were different, and we detected that, like other variants that circulate more strongly not only in Mexico but in the world, they coincide with a series of mutations in the spicule that have an improved escape capacity for the virus; in other words, it is easier for them to reinfect people who already have a certain level of immunity,"  explained García López.

The appearance of BW.1 was in July 2022, during the fifth wave of COVID-19. Its accelerated growth can be explained, in part, by relevant escape mutations also found in BQ.1.

"Being an area of very high capacity for tourism, it has not only remained in Mexico, but we have already detected it in Israel, the United States, France, and even in Japan, probably from people who were tourists in the Mayan area," García López explained.

Scientists think that the BW.1 variant will compete for a few weeks in the middle of the country with BQ.1 and its offspring, which are some of the most successful strains we know of so far. These strains are currently found mostly in the north and center of the country. This will happen at the same time as a new rise in cases at the end of 2022. In the Yucatan Peninsula, in contrast, the BW.1 variant has had months of a head start and is likely to slow the expansion of the BQ.1 lineage.

The increase in COVID-19 cases in southeastern Mexico in October 2022, which ended a period of low transmission after Mexico's fifth epidemiological wave, happened at the same time that the BW.1 variant grew quickly.

Even so, it is important to note that all of the current variants are descended from omicron. Omicron is known for causing mild disease in most people, but it is still a risk for older people, children, and people with high blood pressure, diabetes, or obesity.

The prevalence of the virus has a lot to do with what happens in the world because there is no sanitary fence in Mexico and, instead, there is free entry of tourists from other countries who arrive at a time when there is a wave caused by a certain variant. By bringing it in and taking it to a place where rules have been loosened, the virus continues to change as it moves through Mexico. Some of these changes may help the virus evolve in the long run.

The existence of the variant is not reported directly to the World Health Organization. Instead, it is reported through genomic surveillance to the National Institute of Diagnosis and Epidemiological Reference, which then reports it to the Ministry of Health. The Ministry of Health and the National Institute of Diagnosis and Epidemiological Reference perform the interface.

"One of the things we have learned in the pandemic is that if we deposit all the information in public and international databases, the WHO can carry out independent studies and see which variants are dominating in the world or not," Sanchez Flores explained.

Sequencing these different strains provides them with the genomes, allowing them to track the pathogen's spread almost in real-time, which had never been done before the pandemic.

So far, the official name of the variant is BW.1, and the population mustn't relax its guard against COVID-19 in summer and winter when there is a greater accumulation of cases, as the lessons learned from 2020 to date reaffirm that vaccines, ventilated spaces, healthy distances, use of masks, hand washing with soap, and exposure as little as possible continue to be the best tools against the virus.