Many experts believe variants are largely driving the recent upticks in COVID-19 cases across the U.S., with the B.1.1.7 variant, first identified in the U.K., now accounting for about 26 percent of all U.S. infections, according to recent CDC estimates.
The variant, which is between 50 and 70 percent more transmissible, is the predominant strain in at least five regions of the country, according to Rochelle Walensky, MD, CDC director.
States such as Florida, Texas and Michigan are reporting especially troublesome trends and are currently experiencing some of the highest variant caseloads.
The CDC currently lists five "variants of concern," defining them as ones "for which there is evidence of an increase in transmissibility, more severe disease (increased hospitalizations or deaths), significant reduction in neutralization by antibodies generated during previous infection or vaccination, reduced effectiveness of treatments or vaccines, or diagnostic detection failures."
The agency's three-tier classification system has "variant of high consequence" as the most worrisome group, followed by "variant of concern" and then "variant of interest." No variant is currently considered a variant of high consequence.
Here's a breakdown of the five "variants of concern," as outlined by the CDC:
B.1.1.7, first detected in the U.K.:
- About 50 percent more transmissible
- Likely causes increased disease severity based on hospitalizations and case fatality rates
- Minimal effect on neutralization by monoclonal antibody therapeutics authorized by the FDA for emergency use
- Minimal effect on neutralization by antibodies generated during previous infection or vaccination
- The U.S. has reported 12,505 cases of this variant as of April 1, with Florida (2,351), Michigan (1,237) and Colorado (894) recording the highest number of cases.
P.1, first detected in Brazil and Japan:
- No information provided regarding transmission
- No information provided regarding disease severity
- Moderate effect on neutralization by monoclonal antibody therapeutics authorized by the FDA for emergency use
- No information provided regarding the effects of past infection or vaccination
- The U.S. has reported 323 cases of this variant as of April 1.
B.1.351, first detected in South Africa:
- About 50 percent more transmissible
- No information provided regarding disease severity
- Moderate effect on neutralization by monoclonal antibody therapeutics authorized by the FDA for emergency use
- Moderate reduction in neutralization by antibodies generated during previous infection or vaccination
- The U.S. has reported 224 cases of this variant as of April 1.
B.1.427, first detected in California:
- About 20 percent more transmissible
- No information provided regarding disease severity
- Significant effect on neutralization by some, but not all, therapeutics authorized by the FDA for emergency use
- Moderate reduction in neutralization by antibodies generated during previous infection or vaccination
- The CDC is not yet providing national case counts for this variant.
B.1.429, first detected in California:
- About 20 percent more transmissible
- No information provided regarding disease severity
- Significant effect on neutralization by some, but not all, therapeutics authorized by the FDA for emergency use
- Moderate reduction in neutralization by antibodies generated during previous infection or vaccination
- The CDC is not yet providing national case counts for this variant.