#16,652
Yesterday, in China CDC Weekly Perspective: The “Wolf” Is Indeed Coming: Recombinant “Deltacron” SARS-CoV-2 Detected, we looked at an ominously worded perspective - published this week in China's CDC Weekly - on the detection of, and potential risks from, a `Deltacron' variant reported by China.`Deltacron' is an unofficial moniker, as the WHO has not yet assigned this variant a name, or declared it to be a VOC (Variant of Concern).
Despite an increasing number of `Deltacron' reports around the world, in absolute terms the number of cases reported remains very small, and we've yet to see any evidence to suggest that Deltacron can compete successfully against Omicron, or that it produces more severe illness than BA.1 or BA.2.
While the media is primarily focused on the `Deltacron' angle, the real story here is this is a proof of concept; evidence that (as previously suspected) SARS-CoV-2 can evolve via recombination.
Given the number of non-human hosts susceptible to SARS-CoV-2 infection (see WHO/FAO/OIE Joint Statement On Monitoring SARS-CoV-2 In Wildlife & Preventing Formation of Reservoirs), and the number of other non-COVID coronaviruses in the wild (e.g. SARS-CoV, MERS-CoV, hCoVs, ect.), that ability could allow COVID to evolve in unpredictable ways.
This week, the World Health Organization's Weekly COVID Epi Report (#84) carried the following brief statement on the recombinant COVID variants they are following, where they stress that `None of the preliminary available evidence indicates that these recombinant variants are associated with higher transmissibility or more severe outcomes.'
Recombination of variants of the same virus is a natural phenomenon and can be regarded as an expected mutational event. WHO has been notified of several recombinant variants, either recombination between Delta and BA.1 variants, or BA.1 and BA.2 variants. The same monitoring and assessment process is applied to these recombinants as for any other emerging variant, after verification and exclusion of potential contamination or co-infection.
Two Delta and Omicron recombinants and one BA.1 x BA.2 recombinant have now been given Pango lineage designations XD, XE and XF. None of the preliminary available evidence indicates that these recombinant variants are associated with higher transmissibility or more severe outcomes. WHO continues to monitor recombinant variants, alongside other SARS-CoV-2 variants, and will provide updates as further evidence becomes available.
While they characterize recombination as a `natural phenomenon' and an `expected mutational event', until recently, it really hasn't been part of the `COVID discussion'. It was only two weeks ago (see WHO Weekly COVID Epi Report (#82) & Omicron Review) that the WHO reported they were `aware' of reports of recombinant COVID variants.
Both the Technical Advisory Group on SARS-CoV-2 Virus Evolution (TAG-VE) and WHO are aware of reports on recombinant variants, both recombinants of Delta and Omicron, as well as recombinants of BA.1 and BA.2.
This week's WHO Epi update also indicates that COVID cases continue to rise globally for the second week in a row, but deaths continue to fall. Their summary follows.
Data as of 20 March 2022
After a consistent decrease since the end of January 2022, the number of new weekly cases rose for a second consecutive week, with a 7% increase reported during the week of 14 through 20 March 2022, as compared to the previous week. The number of new deaths has continued a decreasing trend (-23% as compared to the previous week) (Figure 1). Across the six WHO regions, over 12 million cases and just under 33 000 deaths were reported (Table 1). As of 20 March 2022, over 468 million confirmed cases and just over 6 million deaths have been reported globally.At the regional level, the number of new weekly cases increased in the Western Pacific Region (+21%), remained stable in the European Region, and decreased in the Eastern Mediterranean (-41%), Africa (-33%), South-East Asia (-23%) and Americas (-17%) regions. On the other hand, the number of new weekly deaths increased in the Western Pacific Region (+5%), while decreasing in the other regions: Americas (-42%), Eastern Mediterranean (-38%), Africa (-19%), Europe (-18%) and South-East Asia (-18%).
These trends should be interpreted with caution as several countries are progressively changing their testing strategies, resulting in lower overall numbers of tests performed and consequently numbers of cases detected.
At the country level, the highest number of new weekly cases were reported from the Republic of Korea (2 817 214 new cases; +34%), Viet Nam (1 888 694 new cases; +13%), Germany (1 538 666 new cases; +14%), France (582 344 new cases; +39%), and Australia (513 388 new cases; +161%).
The highest number of new weekly deaths were reported from the Russian Federation (3 681 new deaths; - 9%), the United States of America (3 612 new deaths; -58%), Brazil (2 242 new deaths; -32%), the Republic of Korea (2 033 new deaths; +41%), and China (1 921 new deaths; -2%).
Whether or not recombination will produce a more problematic COVID variant remains to be seen. The `fitness' bar for new COVID strains is currently very high, meaning most new variants won't be able to compete with the highly transmissible ones already in circulation.
And it is far from guaranteed that even if a more `biologically fit' recombinant were to emerge, that it would be more severe than past variants.
But recombination gives coronaviruses another tool by which they can reinvent themselves. And that could - in the long run - generate new, and potentially more dangerous, pandemic threats.
Threats we need to be prepared to meet.
