Two COVID-19 mutant strains have been circulating in rising numbers in New York and Colorado during the last three months, prompting fears that they could further spread the coronavirus, according to the Centers for Disease Control and Prevention on Wednesday.
A new COVID-19 variant became the predominant one in circulation in New York City by early April and it tends to infect younger adults, according to one of two new studies published by the CDC.
Since early March, the strain, called B.1.526, has accounted for up to 45% of new infections in the city, up from 3% at the start of the year.
However, just over 4% of those infected with the strain required hospital care and less than 1% died from the disease, the CDC said.
These numbers were identical among other strains found in the city during the first four months of the year, with the exception of the so-called “British” version, or B.1.1.7, which hospitalised 6% of those affected, according to the department.
Less than 1% of people afflicted with the B.1.526 strain were entirely vaccinated, which meant they had administered all doses of either the Pfizer-BioNTech or Moderna vaccines, or the single-dose Johnson & Johnson product.
“Preliminary evidence suggests that, to date, B.1.526 does not lead to more severe disease or increased risk for infection after vaccination,” the CDC researchers wrote.
The B.1.526 variant was first identified in New York City in November, according to the CDC.
The findings of this analysis are based on genetic sequencing of nearly 10,000 samples collected from people infected with the coronavirus between Jan. 1 and April 5.
During that period, there were about 360,000 confirmed cases in New York City, based on estimates from its Department of Health.
The numbers indicate, however, that new daily case reports have been on a largely downward slope since early April, and state and city officials last week unveiled plans to lift pandemic controls designed to prevent virus transmission, including restaurant closures.
According to the CDC researchers, the sequencing tests showed a particular genetic mutation called E484K, which was present in 56 percent of the samples studied.
While this mutation indicates that the virus is still evolving, its appearance “does not lead to more severe disease and is not associated with increased risk for [new] infection or reinfection compared with other [strains],” the researchers wrote.
A separate genetic sequencing analysis, also released by the CDC on Wednesday, confirmed that the B.1.427 and B.1.429 strains first identified in Southern California in January were found in 327 infected with the virus in Colorado as of March 31.
According to the department, these strains are 20% more transmissible, or infectious, than others, and do not react as well to treatment with monoclonal antibodies (drugs modelled on human immune calls).
According to the CDC, there is no evidence that commercially available vaccines are less successful against these variants.