Doctors and researchers still have much to learn about the exact symptoms caused by COVID-19, but a group of ear, nose and throat doctors now suspect two such symptoms may be an altered sense of taste, called dysgeusia, and a loss of smell, known as anosmia.
In a statement released earlier this week, the American Academy of Otolaryngology Head and Neck Surgery reported: "Anecdotal evidence is rapidly accumulating from sites around the world that anosmia and dysgeusia are significant symptoms associated with the COVID-19 pandemic. Anosmia, in particular, has been seen in patients ultimately testing positive for the coronavirus with no other symptoms."
But many other viral infections, including the common cold, similarly can impair one's senses. About 40% of patients recovering from a viral illness report a loss of smell, according to Dr. D.J. Verret, who's double board certified in otolaryngology, head and neck, and facial plastic surgery.
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"The sense of taste and smell are very closely related," he said. "We know from previous research that coronavirus infections are seen in post-viral anosmia. It is therefore not a stretch to think that COVID-19, caused by a coronavirus, can result in smell or taste disturbances."
According to a case report from Taiwan, a woman infected with SARS, a close cousin of COVID-19, lost her sense of smell for more than two years. There isn't yet significant data linking COVID-19 to altered senses of smell or taste, but the anecdotal evidence is growing.
"The good news is that the symptoms seem to be self-limiting and improve with time," said Dr. Wendy Smith, an otolaryngologist at Permanente Medical Group. "Up to two-thirds of post-viral anosmia cases resolve spontaneously. This typically occurs within six to 12 months. Cases related to COVID19 may resolve more quickly."
ENT U.K. at The Royal College of Surgeons of England, a professional society of ear, nose and throat physicians, has reported a significant number of COVID-19 patients from South Korea, China, Germany and Italy experienced a decreased or lost sense of smell -- as many as 30% in South Korea, where patients said it was accompanied by milder symptoms.
Doctors in countries where COVID-19 has spread have reported that some people whose only apparent symptom is a loss of smell may not have been tested for the virus and could unwittingly be spreading it.
But many other individuals experience a loss of smell for afflictions wholly unrelated to COVID-19: nasal and sinus disease, head trauma, Alzheimer's, Parkinson's, stroke, brain tumors, aging, certain medications, tobacco, diabetes, hypothyroidism and exposure to chemical, toxins or metals.
With spring approaching, seasonal allergies also could be the cause of someone's lost or altered senses of smell or taste.
The American Academy of Otolaryngology Head and Neck Surgery wants the loss of smell and altered taste added to list of symptoms considered for COVID-19 screenings. And doctors who see such patients may need to consider self-isolating until tested and cleared of COVID-19.
"Without adequate testing, I don't think you can know for sure," Verret added. "My advice would be to self-quarantine if you have new onset of these symptoms, and be sure to let any healthcare providers you come into contact with know that you have the symptom."
The Centers for Disease Control and Prevention lists symptoms of the new coronavirus as fever, cough and shortness of breath, and that there's currently no treatment or vaccine. Anyone not in immediate distress or requiring emergency attention should stay home and alert a doctor.
Angela N. Baldwin M.D., M.P.H., is a pathology resident at Montefiore Health Systems in New York City and a contributor to the ABC News Medical Unit.
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