The usual symptoms of COVID-19 are fever, cough, fatigue, and sometimes shortness of breath. But as the highly contagious disease continues to infect millions of people, less common signs are being observed.

One of these may be nosebleeds, according to Healthline. The reason why the virus may cause a bloody nose is that researchers have confirmed that COVID-19 gains entry into our cells by attaching itself to ACE-2 receptors. The tissues in our noses have the highest concentrations of these ACE-2 receptors than any other part of the respiratory tract.

If the virus enters the nasal passage and triggers inflammation, this could cause the nose to bleed, according to Healthline. A small study last August tested 40 people who arrived at a hospital with nosebleeds. After swabbing their noses for a COVID-19 test, researchers found that 15 of the people with bloody noses tested positive for the virus, while only 2.5 of a control group of 40 people without nosebleeds had COVID-19.

The statistically significant difference in frequency of bleeding between study subjects and the control group led researchers to speculate that nose bleeds could be a symptom of COVID-19. Other studies have observed similar patterns.

Healthline reports that people who have COVID-19 and are put on oxygen may also have an increased risk of getting nosebleeds because of the increased nose dryness and injury to the tissue that occurs when a cannula is inserted. Researchers found that 30 out of 104 people admitted to the hospital with COVID-19 suffered epistaxis, or bleeding from the nostril, which was attributed to the high frequency of oxygen use.

Additionally, although rarely, some people get nosebleeds after they have been swabbed for a COVID-19 test. More commonly, COVID-19 affects the nose by triggering loss of smell. About 79.6% of sufferers reported a loss of smell in a study that examined nasal symptoms caused by COVID-19.

According to the Washington University School of Medicine in St. Louis, anosmia is the technical term for the temporary or permanent loss of smell. Dr. Jay Piccirillo, an ear, nose, and throat expert in St. Louis, said that for 95% of COVID-19 patients the anosmia usually lasts two to three weeks, but there is a chance it may never return. He estimates that between 40% and 60% of COVID-19 patients experience loss of smell during the initial and acute phases of the disease, and about 5% still suffer from anosmia after three months.

While several small studies have linked COVID-19 to nosebleeds, experts told Healthline that larger studies are needed to confirm the association.