Millions of people have contracted the COVID-19 virus since the pandemic broke out in late 2019.
The World Health Organization counts 190 million people who have been infected.
Many more people, however, are likely to have caught the virus without ever testing positive.
PCR and DPI tests can determine whether a person has an active COVID-19 infection, while antibody tests can show with high certainty whether someone has been infected in the past.
But even if someone did not test positive, some symptoms can hint at whether or not they had caught the virus.
Maladies affecting the eyes are some of the lesser-known symptoms of COVID-19 infection.
Eye symptoms are usually accompanied by more typical COVID-19 symptoms, according to Healthline, but they may also appear alone.
Some symptoms of COVID-19 affecting the eyes include pink eye, dry eyes, excessive tears, and increased secretions.
Loss of smell
Loss of taste and smell are some of the telltale signs of COVID-19 infection.
Some people report these symptoms being permanent after the worst of the infection has passed.
For many, loss of taste and smell is only temporary. Others still report that certain things end up smelling or tasting different from how they did before infection.
Rather than being related to how the virus affects the respiratory system, loss of taste and smell are linked to how COVID-19 affects the brain.
As well as affecting taste and smell, many COVID-19 patients also reported increased levels of anxiety and depression after contracting the virus.
The mental health effects of COVID-19 have also been reported by people after the main symptoms have passed.
Some of the most common symptoms associated with COVID-19 are similar to those caused by the common flu.
These include coughing, fatigue, a runny nose, body aches, nausea, fever, and chills.