Some patients with the new coronavirus have shown gastrointestinal symptoms as the first sign of illness instead of the classic symptoms, according to a new study. For these patients, respiratory symptoms show up only later in the illness.

The paper published in The American Journal of Gastroenterology states that some COVID-19 patients experience diarrhea as the first sign and some never develop respiratory symptoms at all. The findings are important because those without classic symptoms of COVID-19 may go undiagnosed and could potentially spread the illness to others, the researchers said. Classic symptoms of COVID-19 include cough, shortness of breath and fever.

While digestive problems are common overall, doctors should recognize that sudden digestive symptoms in people with a possible COVID-19 contact "should at least prompt consideration of the illness," the authors wrote in their paper. "Failure to recognize these patients early and often may lead to unwitting spread of the disease."

In the new study, the researchers analyzed information from 206 patients at Union Hospital, Tongji Medical College in Wuhan, which was designated as a hospital for COVID-19 patients. Overall, 48 patients (23 percent) were admitted with digestive symptoms only, 89 (43 percent) with respiratory symptoms only and 69 (33 percent) with both respiratory and digestive symptoms.

Among all patients with digestive symptoms (117 patients), about 67 (58 percent) had diarrhea, and of these, 13 (20 percent) experienced diarrhea as the first symptom of their illness. Patients' diarrhea lasted from one to 14 days, with an average duration of five days, the report said. About one-third of patients with digestive symptoms never experienced a fever, the report added, according to Live Science.

Overall, "these data emphasize that patients with new-onset diarrhea after a possible COVID-19 contact should be suspected for the illness, even in the absence of cough, shortness of breath, sore throat or even fever," the authors concluded. "Optimally, testing for COVID-19 should be performed using both respiratory and stool samples, if available."

The study found that those with digestive symptoms tended to seek health care later than those with respiratory symptoms, an average of 16 days from the start of their symptoms, compared with 11 days for those with respiratory symptoms. This is where the concern arises as the people with mild to no classic symptoms but suffering from digestive symptoms might not get themselves checked and the chances of them spreading the virus increases.

The latest study is not the first to report digestive symptoms as a sign of COVID-19. A study posted on March 18 in the same journal found that, among about 200 COVID-19 patients at three hospitals in Wuhan, China, around 50 percent reported at least one digestive symptom, and 18 percent reported diarrhea, vomiting or abdominal pain. However, this study tended to focus on patients with severe illness, rather than those with mild disease.

Meanwhile, the authors of the latest study mentioned that their study was relatively small, and larger studies are needed to further describe digestive symptoms in patients with mild COVID-19.