They’re called the “long-haulers” — the people who suffer from debilitating coronavirus symptoms for months.

In March, when many long-haulers were first falling sick with gut, heart and brain problems, experts were looking only at respiratory signs of COVID-19 and missed their symptoms. Even today, the Centers for Disease Control and Prevention lists only loss of taste or smell as neurological symptoms of the disease.

According to The Atlantic, people suffering from extended COVID-19 illness have experienced a wide range of symptoms, including hallucinations, delirium, irregular heartbeats and difficulty breathing.

“It is really a grab bag,” Hannah Davis, an artist from New York City, told The Atlantic. “Every day you wake up and you might have a different symptom.”

Experts only have theories why some people defy statistics and end up sick for months. Akiko Iwasaki, an immunologist at Yale, told The Atlantic that it could be that long-haulers still harbor infection in an organ. Or, he said, there could be fragments of viral infection that linger, causing the immune system to overreact.

One long-hauler, Fiona Lowenstein, created a support group for people struggling with the disease.

“My recovery from the disease dragged on for more than seven weeks,” she told Vox. “In the absence of public health information, I connected with other COVID-19 survivors and started the Body Politic COVID-19 support group for people living with the virus.

“Today, my support group is one of many attempting to meet the needs of people living with the coronavirus,” she said.