What is NB.1.8.1?

In January, a new COVID-19 variant NB.1.8.1 was first detected in China. Since then, there have been 518 reported cases of NB.1.8.1 in 22 different countries, including the United States.

On May 23, the World Health Organization (WHO) designated NB.1.8.1 as a variant under monitoring. As of May 18, NB.1.8.1 made up 10.7% of all COVID-19 cases worldwide. "While still low numbers, this is a significant rise in prevalence from 2.5% four weeks prior."

Although countries with high prevalence of NB.1.8.1 have seen increases in COVID-19 cases and hospitalizations, there is currently no evidence to suggest that NB.1.8.1 causes more severe disease than the other COVID-19 variants currently circulating. So far, symptoms from NB.1.8.1 appear to be similar to earlier COVID-19 variants and include fevers or chills, cough, shortness of breath, loss of smell or taste, and fatigue.

"With each new variant, what we've seen is severity doesn't really change so far, we're not seeing it have more severe complications," said John Brownstein, chief innovation officer at Boston Children's Hospital. 

However, NB.1.8.1 may be more transmissible than other COVID-19 variants, which means it could infect more people more quickly.

"NB.1.8.1. is likely to spread more rapidly and evade our immune defenses more easily than LP.8.1 [the currently dominant variant in the United States], which is why this variant requires careful monitoring," said Subhash Verma, a professor of microbiology and immunology at the University of Nevada, Reno.

"It may unfortunately come back with a little bit of vengeance on us," said Thomas Russo, chief of infectious diseases at the University of Buffalo Jacobs School of Medicine and Biomedical Sciences. "Let's hope that doesn't happen, but I am concerned that we may be setting ourselves up for that with this combination of factors."

Separately, Scott Roberts, associate medical director of infection prevention at the Yale School of Medicine, noted that COVID-19 cases typically increase twice a year in the summer and winter regardless of what variant is circulating.

"I'm going to go ahead and guess that it's [NB.1.8.1] going to lead to an uptick in the summer — probably a mild to moderate one," Roberts said.

In addition, Roberts recommended that people haven't been vaccinated or had COVID-19 recently get a booster shot now if they're eligible. According to WHO, currently approved COVID-19 vaccines are expected to still be effective against NB.1.8.1.

"This is the natural path we've seen with every variant, and so the guidance doesn't really change at the end of the day," Brownstein said. "It's making sure people are up to date with their vaccines and boosters ... and then of course, those that are immunocompromised or in high-risk groups may want to layer in other types of interventions like masking or being careful about large group settings where there could be increased risk of transmission."