More than half of the world’s 236 million COVID patients can expect to suffer from “long haul” type symptoms for up to six months, according to researchers at Penn State College of Medicine. A study by the authors published in the Journal of the American Medical Association on Wednesday relied on dozens of reports published worldwide on unvaccinated COVID-19 patients who recovered from the illness. The researchers looked at each patient’s condition at three separate points: one month after recovery, two to five months later, and six months or later.

They found that more than half of the patients still had symptoms up to six months after recovery, including neurological issues, lung abnormalities, and cardiovascular issues like heart palpitations and chest pain. Others suffered hair loss or skin rashes, some had digestive issues. “The burden of poor health in COVID-19 survivors is overwhelming,” Dr. Paddy Ssentongo, one of the study’s lead researchers, said in a statement. “One’s battle with COVID doesn’t end with recovery from the acute infection.” It remains unclear how or why COVID-19 symptoms can linger in those who have recovered, but the researchers say their findings show a crucial need for health-care systems to prepare for an influx of long haulers.