Potentially deadly fungal infections with Candida auris are spreading rapidly in US healthcare facilities, with cases nearly doubling between 2020 and 2021, the US Centers for Disease Control and Prevention said on Monday.

The number of cases rose by 44% to 476 in 2019, up from 330 in 2018, and subsequently by 59% to 756 in 2020 and by an additional 95% to 1,471 in 2021, the agency’s researchers reported on Monday in Annals of Internal Medicine.

Also concerning was a tripling in 2021 of the number of cases that were resistant to echinocandins, the class of drugs most often recommended for treatment of the disease.

The most common Candida auris symptoms include a high fever and chills that do not improve after antibiotic treatment for suspected bacterial infections, according to guidelines from the CDC. Additional symptoms can develop if the infection spreads.

Dr Waleed Javaid – an epidemiologist, infectious disease expert and director of infection prevention and control at New York’s Mount Sinai Downtown – told NBC News that the new findings were “worrisome”. But they do not mean that the world is about to experience an apocalypse like the one caused by an outbreak of cordyceps fungal infections in the hit fictional HBO series The Last of Us, Javaid said.

“We don’t want people who watched [the TV show] to think we’re all going to die,” Javaid said.

People who are very sick, have invasive medical devices such as mechanical ventilators, or have long or frequent hospital stays are at particular risk for the infections, the report said.

“The rapid rise and geographic spread of cases is concerning and emphasizes the need for continued surveillance, expanded lab capacity, quicker diagnostic tests, and adherence to proven infection prevention and control,” the study’s leader, Dr Meghan Lyman, said in a statement.

The CDC noted that the spread of infections in 2021 may have been exacerbated as the healthcare system was hit by stresses related to the Covid-19 pandemic, including staff and equipment shortages.

The report did not include data from 2022, but the CDC’s website shows 2,377 cases of confirmed Candida auris infections in the US. Last year was a sharp increase from 53 in 2016, when cases were first reported in the country.

Although it was initially limited primarily to the New York City and Chicago metropolitan areas, Candida auris has now been detected in more than half of US states, with recent cases mostly reflecting local transmission of the disease, according to the report.

Other countries have also reported increased spread of the fungus, the researchers said.