While the delta COVID-19 variant is the dominant strain in the U.S., it's now officially the dominant strain worldwide "by far," officials from the World Health Organization said during a Sept. 21 pandemic update.
The highly contagious delta strain has been detected in more than 185 countries, The Washington Post reports. It accounts for more than 99 percent of cases in the U.S., according to the CDC.
Four more updates:
1. Of the WHO's four variants of concern, delta is "outcompeting and replacing" the rest.
"For example, if delta is identified or starts to circulate in a country where there is beta … [delta] has quickly replaced the variant there," said Maria Van Kerkhove, PhD, the WHO's technical lead on COVID-19.
"Less than 1 percent of the [global] sequences that are available right now are alpha, beta and gamma," she said.
2. Delta is also overtaking the WHO's two variants of interest, mu and lambda. In early September, health officials raised concern about mu, first detected in Columbia, when early data indicated it may be more resistant to vaccines than other variants. About 3,300 cases of the mu variant have been detected in the U.S. as of Sept. 11, according to the Global Initiative on Sharing All Influenza Data, which tracks global viral genome data. At its peak in June, mu made up less than 5 percent of all circulating variants in the U.S. It now makes up less than 1 percent of cases in the country, CDC data shows.
Lambda, first detected in Peru, which preliminary data showed was highly transmissible and potentially more resistant to vaccines than earlier strains, is also being replaced by delta. It's been detected in about 1,058 cases in the U.S. as of Sept. 2, GISAID data shows.
"Lambda and mu don't seem to be dominant," Dr. Van Kerkhove said.
3. The WHO also reclassified eta, iota and kappa from variants of interest to variants under 'monitoring' status Sept. 22 — indicating they "no longer pose a major added risk to global public health compared to other circulating SARS-CoV-2 variants."
"They are not taking hold," Dr. Van Kerkhove said.
4. The CDC updated its variant classifications Sept. 21, adding 'variants being monitoried' as a new designation. The CDC's new classification currently includes 10 variants, including eta, iota and kappa, which like the WHO, previously labeled as a variants of interest.
Due to their low prevalence in the U.S., variants being moniored "do not pose a significant and imminent risk to public health in the United States," the CDC said, adding that it "will continue to monitor these variants closely to identify changes in their proportions."