The novel coronavirus has rapidly spread across the globe, infecting 3.58 million, and killing more than 251,000 people. As the disease evolves, there’s a new focus on the symptoms.
Though the two common symptoms are cough and fever, recent studies and reports point to a loss of smell as a symptom early in the disease process. A team of researchers at the Technical University Dresden (TU Dresden) revealed that the sudden loss of smell is experienced by many patients infected with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Their research titled 'Predictive value of sudden olfactory loss in the diagnosis of COVID-19', is published on the preprint server medRxiv*.
The researchers wanted to know the frequency of olfactory loss in an out-patient group of patients who have COVID-19 in two weeks. They want to evaluate the diagnostic value of this particular symptom for screening patients for SARS-CoV-2 infection.
Loss of smell
Many patients who tested positive for SARS-CoV-2 infection reported having no sense of smell and taste. Viruses, in general, may lead to an olfactory loss. A variety of viruses can attack the cranial nerves responsible for olfaction or the mucosal tissue that surrounds the nerves. Cranial nerves are essential nerves in the body since they control the head and neck. For instance, cranial nerves help people speak through the vocal cords, hear, smell, and control their facial motions.
Study: Predictive value of sudden olfactory loss in the diagnosis of COVID-19. Image Credit: Zay Nyi Nyi / Shutterstock
The SARS-CoV-2, a novel type of coronavirus, can cause respiratory symptoms, just like other coronaviruses. Other pathogens, such as influenza and rhinoviruses, also cause loss of the sense of smell. These pathogens induce inflammation, either in the nerve itself or around the nasal lining. Since the nerves are lined with inflammatory molecules, it may impair the ability to smell odors.
Prevalence of olfactory loss
In the study, the researchers analyzed the data and symptoms of 500 patients who had symptoms of common colds. These patients fulfilled novel coronavirus testing criteria and completed a standardized diagnostic questionnaire, which asked for the patient’s symptoms and time course. Additional self-assessment questions were asked, such as current smell and taste function, as well as the presence of nasal breathing.
The researchers revealed that out of the 500 patients, 69 reported loss of smell, and 22 of them subsequently tested positive for COVID-19. Of those without olfactory loss, only 12 patients had a positive coronavirus test result. Further, those who reported a loss of smell, they were younger and less severely affected. Of the 34 patients who tested positive for SARS-CoV-2, 64.7 percent had a sudden loss of smell.
Included in the symptom list
With the high rate of SARS-CoV-2 patients presenting with a sudden loss of smell, it is recommended that the symptom is added to the World Health Organization (WHO)’s symptom list.
“Thus, considering the high frequency of smell loss in non-hospitalized COVID-19 patients, acute olfactory impairment should be included in the WHO symptoms list and should be recognized as an early symptom of the disease. It also suggests the need for an exhaustive olfactory and gustatory follow-up of these patients to assess the extent of the olfactory loss and the significance of the chemosensory loss in terms of the prognosis of the patients,” the researchers concluded in the study.
Most individuals infected with the novel coronavirus will experience mild to moderate respiratory illness. Most of them recover without requiring special treatment. However, older adults, people with underlying medical problems, such as diabetes, chronic respiratory disease, heart disease, and cancer, and those with suppressed immune systems, are at a higher risk of developing severe COVID-19.
The World Health Organization (WHO) reports the most common symptoms of COVID-19, including fever, dry cough, and tiredness. It listed the less common symptoms such as aches and pains, diarrhea, sore throat, conjunctivitis, loss of taste and smell, headache, and a rash or discoloration on the toes or fingers.
Severe COVID-19 cases may present with shortness of breath, the difficulty of breathing, chest pressure or pain, and loss of movement or speech.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.