"COVID-19 had symptoms such as coughs, shortness of breath and high fever before. These symptoms were observed in the first two months after the outbreak. But now the most important symptoms of COVID-19 are gastrointestinal," said Dr. Mohammad-Reza Mahboubfar, a viral epidemiologist and member of the Coronavirus Taskforce, according to Radio Farda.
The shift from respiratory to gastrointestinal symptoms may delay diagnosis of COVID-19 and contribute to the spread of the virus.
Gastrointestinal symptoms include acute diarrhea, abdominal spasms, stomachache, nausea, vomiting, loss of appetite, low fever and loss of taste and smell. These symptoms are now more prevalent in coronavirus patients from various age groups in Iran including the elderly and children.
Dr. Seyed Hassan Abedi, a gastroenterologist of Babol Medical Sciences University, warned about the change in coronavirus symptoms on May 16, saying that fewer patients were being hospitalized with respiratory symptoms, but more patients were suffering from gastrointestinal complications.
According to Abedi, a quarter of all COVID-19 patients only show gastrointestinal symptoms and end up seeking medical care later than those with more pronounced respiratory symptoms.
About one-third of those with gastrointestinal symptoms do not have fevers, but they do have acute diarrhea which can occur at least five times a day and last up to two weeks.
Liver and pancreas damage has also been reported in COVID-19 patients in Iran, according to Radio Farda.
Dr. Seyed Reza Fatemi, a gastroenterologist from Shahid Beheshti University of Tehran, found that up to 50% of coronavirus patients show gastrointestinal symptoms and that the virus can cause liver damage in inflammation of the pancreas in 20%-30% if all patients.
Strokes have also been associated with the virus in Iran. Strokes in children in Iran may also have been caused by the coronavirus.
Dr. Hossein Keivani, professor of virology at Tehran University, told Radio Farda that while the coronavirus may change occasionally and cause atypical symptoms, it doesn't mutate quickly enough to infect those who have become immune again.
A study by Chinese scientists from Wuhan in the Lancet Journal found that 50% of patients they surveyed reported digestive symptoms, such as lack of appetite, diarrhea, vomiting and abdominal pain. Only a few patients in the study did present fever or respiratory symptoms.
Multiple new symptoms have been discovered over the past two months that may be associated with the novel coronavirus, some appearing even without any respiratory symptoms.
Reports from multiple countries have indicated that significant numbers of coronavirus patients experienced anosmia, the loss of sense of smell, and ageusia, an accompanying diminished sense of taste, according to The New York Times.
Some COVID-19 patients are also experiencing neurological issues, including confusion, stroke and seizures, according to the Times. Some patients also reported acroparesthesia, a tingling or numbness in the extremities. Others have been afflicted by symptoms of a serious heart attack, but without any blocked arteries. Dermatological symptoms such as pseudo-frostbite, hives and persistent, sometimes painful redness have also been associated with the virus.
Italian and British medical experts are investigating a possible link between the coronavirus pandemic and clusters of severe inflammatory disease among infants arriving in hospitals with high fevers and swollen arteries.
Studies on many of the newly realized symptoms have not been conducted, as physicians handling the coronavirus outbreak are overwhelmed, according to Forbes.
A study carried out by Professor Li Lanjuan and colleagues from the Zhejiang University in Hangzhou, China and published in a non-peer reviewed paper found that medical officials have vastly underestimated the overall ability of the virus to mutate, in findings that different strains have affected different parts of the world, leading to potential difficulties in finding an overall cure.
Li's team infected cells with COVID-19 strains carrying different mutations, of which the most aggressive strains were found to generate as much as 270 times as much viral load as the weakest strains. The aggressive strains also killed the human cells the fastest.
The results indicated "that the true diversity of the viral strains is still largely underappreciated,” Li wrote.
Alex Winston contributed to this report.