Mario Buelna, a healthy 28-year-old father, caught a fever and started having trouble breathing in June. He soon tested positive for COVID-19. Weeks later, after what had seemed like a recovery, he felt weak and started vomiting. At 3 a.m. on Aug. 1, he passed out on the floor of his home in Mesa, Arizona. Paramedics rushed him to a nearby hospital, where doctors put him in intensive care after saving him from a coma. They told him he could have died. Their diagnosis – type 1 diabetes – stunned and frightened him. He had no history of the disease. “COVID triggered it,” Buelna said the doctors told him. Buelna’s ordeal and similar cases reflect a new worry about the dangerous relationship between diabetes and COVID-19 that’s being urgently studied by doctors and scientists around the world. Many experts are convinced that COVID-19 can trigger the onset of diabetes – even in some adults and children who do not have the traditional risk factors. It’s already been well-documented that people with diabetes face much higher risks of severe illness or death if they contract COVID-19. In July, US health officials found that nearly 40% of people who have died with COVID-19 had diabetes. Now, cases like Buelna’s suggest the connection between the diseases runs both ways. “COVID could be causing diabetes from scratch,” said Dr. Francesco Rubino, a diabetes researcher and chair of metabolic and bariatric surgery at King’s College London. Rubino is leading an international team that is collecting patient cases globally to unravel one of the biggest mysteries of the pandemic. Initially, he said, more than 300 doctors have applied to share cases for review, a number he expects to grow as infections flare up again. “These cases are coming from every corner of the world and every continent,” Rubino told Reuters. In addition to the global registry, the US National Institutes of Health is financing research into how the coronavirus may cause high blood sugars and diabetes. In these situations, symptoms can escalate quickly and become life threatening. These cases may take months to surface after exposure to COVID-19, so the full extent of the problem and the long-term ramifications may not be known until well into next year. More intensive research is needed to definitively prove, beyond the mounting anecdotal evidence, that COVID-19 is triggering diabetes on a wide scale. “We have more questions than answers right now,” said Dr. Robert Eckel, president of medicine and science at the American Diabetes Association. “We could be dealing with an entirely new form of diabetes.” ‘ABSOLUTELY TERRIFYING’ DIAGNOSIS Type 1 diabetes occurs when the body’s immune system mistakenly destroys insulin-producing cells in the pancreas, preventing the regulation of blood sugar levels. About 1.6 million Americans have the disease. Type 2 diabetes is more prevalent, afflicting about 30 million Americans. Those patients still produce insulin, but over time their cells become insulin-resistant, allowing blood sugar to rise. Type 1 diabetes cases have previously been associated with other viral infections, including influenza and previous coronaviruses. It is known that infections can stress the body and increase blood sugar levels. But this tends to happen in people predisposed to the disease. Only some of them eventually develop diabetes, and scientists still don’t fully understand why. This year, doctors also are seeing some people without the risk factors for type 2 diabetes – such as being older or overweight – experience a diabetic emergency after exposure to COVID-19. In type 1 diabetes, initial symptoms can include extreme thirst, fatigue, frequent urination and weight loss. Arthur Simis had no idea those were signs for the disease. This summer, he and his wife, Sarah, noticed their 12-year-old son, Atticus, appeared thin and slept a lot. They figured he was stressed out from being trapped at home in the pandemic, or going through a growth spurt. On July 9, as his symptoms persisted, Arthur Simis took his son to an urgent care center near their home in Gardnerville, Nevada. The medical staff detected dangerously high blood sugar levels and ketones in his urine, both indicators that Atticus was in diabetic ketoacidosis, or DKA. The doctor told Simis that his son needed hospital care immediately to avoid slipping into a coma from his newly diagnosed type 1. An ambulance took them 50 miles to the nearest hospital in Reno. His father spent three nights sleeping at his side in the pediatric ICU. He sobbed on the phone to his wife, because only one parent was allowed inside, a measure to control coronavirus infections. “How could he have diabetes?” Simis recalls asking the doctors. “It was absolutely terrifying.” Simis believes his son had been infected by the coronavirus because the father and his wife experienced symptoms in the spring. The couple went to urgent care but never got tested for the coronavirus because of stricter testing criteria at the time. Atticus tested negative for an active coronavirus infection in the ICU, medical records show. But he was never tested for antibodies that could show whether he was exposed weeks earlier. Doctors say that’s not unusual in a fast-moving pandemic, as they focus on individual emergencies rather than big-picture research questions. But the lack of testing in many of these cases, they say, may complicate efforts to detect whether and how the coronavirus might be causing diabetes. CHILDREN IN INTENSIVE CARE The initial reports of COVID-related diabetes include more children with cases like that of Atticus. In a study published in August, researchers at Imperial College in London and several hospitals there found that cases of type 1 diabetes among children nearly doubled to 30 during late March to early June – as the pandemic raged – compared to the same period in previous years. Five of the children tested positive for a prior coronavirus infection, but the study’s authors said many of the children were not tested. In the United States, Children’s Hospital Los Angeles said the percentage of newly diagnosed type 2 patients who arrived in diabetic ketoacidosis, a potentially fatal buildup of acid in the blood, has nearly doubled for March through August compared to the same period in 2018 and 2019. Dr. Lily Chao, director of the type 2 diabetes clinic there, said the hospital is still investigating whether this increase is driven by exposure to COVID-19. Brandi Edwards, a registered nurse and diabetes educator at Alabama’s Huntsville Hospital, said calls about pediatric cases began to surge in May. Doctors summon her when a child arrives in the emergency room or ICU so she can counsel the family on insulin injections, glucose readings and how daily life will change going forward. “We’ve seen more type 1 cases this year than I ever remember,” Edwards said. “There were three kids in the pediatric ICU at the same time. That is so rare.” EVICTION NOTICE After surviving a diabetic emergency, life for a newly diagnosed patient can be overwhelming. Medication and other supplies to manage diabetes can cost hundreds of dollars every month, and long waits to see an endocrinologist are common in many areas. Buelna, the patient in Arizona, is still waiting for his Medicaid plan to approve a continuous glucose monitor more than two months after his diagnosis. The disease knocked him out of work for weeks and wrecked his family’s finances. His wife, Erika, is eight months pregnant and they have a 3-year-old daughter, Katalina. The family got an eviction notice on Aug. 2, while Mario was in the ICU, and they rely on a food bank for some meals.