How long after losing taste and smell are you contagious

A display of spices lends color to a section of the Fancy Food Show in New York City. Doctors are ... [+] reporting that people infected with the pandemic virus may lose their sense of smell and perhaps taste. (AP Photo/Seth Wenig, File)

Loss of smell and taste is an unusual and relatively recently reported symptom of COVID-19 infection. Should patients with that as a new symptom, called anosmia, self-isolate?

A new study helps answer that question. Ahmad Sedaghat, associate professor of otolaryngology at the University of Cincinnati, and colleagues undertook a major literature review, reported in Laryngoscope Investigative Otolaryngology. Of 2013 studies through March 28 that they screened, they identified nineteen as having full text available with detail needed for analysis. Importantly, in a French study they cite, 94% of patients who presented complaining of isolated anosmia tested positive for COVID-19; the others had risk factors that suggested the tests might have been falsely negative, one problem that has plagued the testing.

Sedaghat concluded that patients with smell loss and no runny nose or stuffiness (that would be common with a cold) should self-isolate. He also notes that “nasal shedding of live virus is usually quite high early in the course of COVID-19, precedes lower respiratory tract viral shedding and may even continue after virus is no longer detected from the lower respiratory tract.” They suspect that prolonged shedding might occur, even after apparent recovery. This is part of what makes COVID-19 so infectious.

One example of the risk of nasal secretions is a cluster of infections that occurred among hospital staff following pituitary surgery, which is done through the patient’s nose, drilling through bone into the skull. Those surgical procedures generate infective aerosols.

When do symptoms occur?

The loss of smell (and often taste as well) occurs early in the illness, according to some. But most doctors and nurses are too overwhelmed by their patient loads and being short-staffed to carefully note the time course of symptoms, and patients are poor at remembering.

German virologist Hendrik Streek carefully followed an early cluster of cases in Germany, doing daily clinical assessments and lab studies. Two thirds of his patients described a loss of smell and taste lasting several days.His patients thought it occurred a bit later in the course of infection. Massimo Galli,⁠Professor of Infectious Diseases at the University of Milan, also noted the anosmia occurred too late to be used for a diagnostic sign.

Interestingly, researchers at Kings College London have an app to track the development of symptoms in Brits, even if they initially have no symptoms. They found that of patients who later tested positive for COVID-19, 60% had lost their sense of smell. This was more specific even than fever. Claire Hopkins, president of the British Rhinological Society, noted that anosmia should alert health care workers to use additional personal protective equipment (if they have it). In Hopkins’ series, 25% lost their sense of smell before developing any other symptoms and 25% at the same time as other symptoms. Half the patients lost smell later in the course. She also noted that if patients with anosmia self-isolate, this might help us reduce transmission.

How long the loss of smell lasts is also not clearly known. In the German study, above symptoms cleared after about two weeks, according to Dr. Clemens Wendtner. Streek said the symptoms lasted “several days.” Some patients I have heard about have complained of anosmia lasting more than a month, though this is apparently a bit of an outlier.

The problem with relying on loss of smell as an alarm is that a person who might be infected with SARS-CoV-2, the virus that causes COVID-19 infection, might develop that symptom too late in their course for it to be all that helpful.

Another problem is that loss of smell occurs in almost a third of patients with more common respiratory tract infections. Some patients with COVID-19 also had runny noses or stuffy noses. So, nothing is an absolute indicator of infection.

Some people with allergies will also complain of some loss of smell, but they usually have a runny nose or sneezing. If you have a fever, then you know you have an infection, not an allergy.

What should you do?

Estimates are that at least 15% of people with COVID-19 will lose their sense of smell.

Most people in the US still cannot be tested to diagnose COVID-19. Hospital emergency rooms and urgent care centers are overwhelmed. Please don’t add to their burden just to see if you have COVID-19. Only go if you are having trouble breathing or having serious symptoms (or a heart attack, trauma, etc.)

Sedaghat concludes, “The real significance of anosmia is as a public health tool, as a predictor of the (tentatively) 25-35% of COVID-19 patients who have anosmia as a first symptom but don’t recognize that they have COVID-19, so they continue to go about business as usual and potentially infect others.”

Each of these experts agrees, “If you’ve lost your sense of smell or taste, self-isolate” to protect others, even if you don’t have other symptoms.

Full coverage and live updates on the Coronavirus

Are you contagious after losing taste and smell?

When is Covid no longer contagious?

Are you still contagious after 7 days of Covid?

Are you still contagious after 5 days of Covid?