The number of COVID-19 cases is increasing in parts of the U.S. and worldwide amid the emergency of a sub-variant known as "razor blade throat COVID."

The variant — NB.1.8.1. or “Nimbus” – got the nickname because it can cause painful sore throats. 

The number of reported cases of COVID began increasing in May – primarily in the eastern Mediterranean, Southeast Asia and western Pacific regions, according to the World Health Organization. And roughly 11% of the new cases have been attributed to the new variant.

Airport screening in the United States detected the new variant in travelers arriving from those regions in California, New York and Washington state, according to the Associated Press. 

Nimbus symptoms havealso been identified by doctors in the United Kingdom and India, according to media outlets in those countries, the wire service also reports.