A new variant has been labelled as "under monitoring" by the following a spike in cases and .

First identified on January 22 2025, NB. 1.8.1 is a derivative of the strain. The variant is causing concern among health experts after being identified in multiple countries including popular holiday destinations like Egypt, Thailand and the Maldives.

The WHO has warned that the new strain is now responsible for more than 10 per cent of all infections and is already the dominant strain in Hong Kong and . The Centre of Disease Control (CDC) in the US has also identified cases in a number of states including New York, California, Arizona, Ohio, Washington, and Rhode Island.

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Despite saying that the variant is currently being monitored, WHO said in their report that the current risk to the public is deemed to be low - and currently approved vaccines are expected to "remain effective to this variant against symptomatic and severe disease." WHO said that despite an increase in cases and hospitalisations, currently there is no indication that this variant leads to more severe illness than other variants in circulation.

Even though NB.1.8.1 has been found in popular holiday destinations, the WHO says there is no need for travel or trade restrictions at this time, reports. The organisation urges countries to stay alert and adjust their responses as needed, but does not recommend closing borders or limiting travel.

The official report states: "WHO recommends that countries remain vigilant, adapt to evolving epidemiological trends, and leverage Covid-19 management strategies to strengthen systems for all respiratory disease threats. Member States should continue offering Covid-19 vaccines in line with WHO recommendations."

Health experts at the CDC say that symptoms may vary in accordance with the variant, however they will likely be similar to the typical symptoms of Covid-19. These include fever or chills, cough, shortness of breath or difficulty breathing, , congestion or runny nose, new loss of taste or smell, fatigue, muscle or body aches, headache, nausea or vomiting, diarrhoea.

This week, Lara Herrero Associate Professor and Research Leader in Virology and Infectious Disease at Griffith University, said that thanks to multiple mutations, the new strain "may infect cells more efficiently than earlier strains." Professor Herrero explained: "It's possible a person infected with NB.1.8.1 may be more likely to pass the virus on to someone else, compared to earlier variants. The evidence so far suggests NB.1.8.1 may spread more easily and may partially sidestep immunity from prior infections or vaccination. These factors could explain its rise in sequencing data.

"But importantly, the WHO has not yet observed any evidence it causes more severe disease compared to other variants. Reports suggest symptoms of NB.1.8.1 should align closely with other subvariants. Common symptoms include , fatigue, fever, mild cough, muscle aches and nasal congestion. Gastrointestinal symptoms may also occur in some cases."

The WHO report reads: "SARS-CoV-2 continues to evolve, and between January and May 2025, there were shifts in global SARS-CoV-2 variant dynamics. At the beginning of the year, the most prevalent variant tracked by WHO at the global level was XEC, followed by KP.3.1.1. In February, circulation of XEC began to decline while that of LP.8.1 increased, with the latter becoming the most detected variant in mid-March. Since mid-April, the circulation of LP.8.1 has been slightly declining as NB.1.8.1 is increasingly being detected."