Credit CDC
#15,717
Less than 3 weeks ago Colorado reported the first confirmed case of COVID variant B.1.1.7 in the United States, followed quickly by announcements from California, Florida, New York, and Georgia.
Since then a total 16 states have reported 88 cases. These numbers undoubtedly under-represent the true spread of this variant by a long shot.
Genomic sequencing is only done for about 1 in every 330 positive US cases right now - and these test results can be delayed for a week or longer - meaning the real number of domestic likely already runs into the thousands.
Even though the total cases detected remains small (n=88), yesterday's MMWR (see Emergence Of SARS-CoV-2 B.1.1.7 Lineage — United States, Dec 29, 2020–Jan 12, 2021) cautioned that this prolific variant could become dominant by March.
And this is just the B.1.1.7 variant. Testing and surveillance for two more variants of concern - one (501Y.V2) originating in South Africa, and the other (P.1) in Brazil - have only just begun. Neither have been detected in the United States, but the odds favor that one or both have already arrived.
Yesterday the CDC updated their interactive map, indicating that 16 states have now verified a total of 88 B.1.1.7 variant infections. California leads with 40 cases, followed by Florida with 22.
While the full impact of these variants (and presumably others to come) is unknown, each has demonstrated enhanced transmissibility, which could greatly increase the number of infected over the next few months.
The CDC explains why tracking, and slowing the spread, of these emerging variants is so important:
CDC has been conducting SARS-CoV-2 Strain Surveillance to build a collection of SARS-CoV-2 specimens and sequences to support public health response. Routine analysis of the available genetic sequence data will enable CDC and its public health partners to identify variant viruses for further characterization.Viruses generally acquire mutations over time, giving rise to new variants. For instance, another strain recently emerged in Nigeria[1]. CDC also is monitoring this strain but, at this time, it has shown no characteristics of greater concern to public health experts.Some of the potential consequences of emerging variants are the following:
- Ability to spread more quickly in people. There is already evidence that one mutation, D614G, confers increased ability to spread more quickly than the wild-type[2] SARS-CoV-2. In the lab, 614G variants propagate more quickly in human respiratory epithelial cells, outcompeting 614D viruses. There also is epidemiologic evidence that the 614G variant spreads more quickly than viruses without the mutation.
- Ability to cause either milder or more severe disease in people. There is no evidence that these recently identified SARS-CoV-2 variants cause more severe disease than earlier ones.
- Ability to evade detection by specific diagnostic tests. Most commercial polymerase chain reaction (PCR) tests have multiple targets to detect the virus, such that even if a mutation impacts one of the targets, the other PCR targets will still work.
- Decreased susceptibility to therapeutic agents such as monoclonal antibodies.
- Ability to evade natural or vaccine-induced immunity. Both vaccination against and natural infection with SARS-CoV-2 produce a “polyclonal” response that targets several parts of the spike protein. The virus would likely need to accumulate multiple mutations in the spike protein to evade immunity induced by vaccines or by natural infection.
Among these possibilities, the last—the ability to evade vaccine-induced immunity—would likely be the most concerning because once a large proportion of the population is vaccinated, there will be immune pressure that could favor and accelerate emergence of such variants by selecting for “escape mutants.” There is no evidence that this is occurring, and most experts believe escape mutants are unlikely to emerge because of the nature of the virus.
As the CDC explains, none of these variants has been shown to evade the current vaccine, although two (501Y.V2 and P.1) carry the E484K mutation, which has been linked to reduced antibody recognition.
Further testing will be needed to determine how much of an effect - if any - this mutation will have on monoclonal antibody therapies, vaccines, or reinfection rates.
In the meantime, even without these other potential complications, a significantly more transmissible SARS-COV-2 virus provides more than enough challenges for a pandemic-weary world.
And from what we've seen in recent weeks, COVID seems determined to evolve in that direction.
