Health experts admit there’s still a lot we don't know about the COVID-19 pandemic that has slammed the world for months.

For example, there is conflicting evidence about how it’s spread and why it can cause a wide variety of symptoms. We don’t know how many people have been actually infected or why it affects some people more severely than others.

Here, according to CNN, are some of the things we do know about the disease:

• Symptoms. We do know that the main symptoms are fever, cough and shortness of breath. Others include headache, muscle ache and fatigue, which are also typical symptoms of the flu. Loss of taste and smell as well as conjunctivitis of the eye have been reported. According to Fox News, some patients have experienced skin rashes, strokes and “Covid-toes,” where the toes develop purple lesions. Shortness of breath along with new mental confusion are symptoms of COVID-19 that signal immediate medical attention.
• Who gets sick? Essentially, we’ve learned that everyone can become ill from the coronavirus, from the elderly to babies in the womb. According to CNN, people of all ages have collapsed and died. White House advisor Dr. Anthony Fauci, a leading infectious disease expert, said in a recent interview with Mark Zuckerberg, CEO of Facebook, that people have been “knocked on their back and brought to their knees pretty quick,” adding that “many, many young people who get infected. They get sick. They feel horrible for weeks and weeks.”
• Medical conditions. We do know that anyone with at least one chronic medical condition, including obesity, is at a higher risk of complications and severity from COVID-19. According to CNN, the Centers for Disease Control and Prevention says that 40% of Americans are obese and 60% of adults have at least one medical condition. Diabetes, heart disease, asthma, and cancer are other conditions that increase the danger of COVID-19. Pregnant women are more likely to land up in intensive care and 70% are more likely to be put on ventilators.
• Transmission. While the vast majority of coronavirus transmission has been from person-to-person, we now know that the virus can linger in the air, potentially infecting people in poorly ventilated spaces.

Last week the World Health Organization acknowledged that the coronavirus may linger in the air in crowded spaces after stating that this type of transmission is unlikely. However, growing scientific and anecdotal evidence prompted the organization to change its stance.

A study published in March in the New England Journal of Medicine stated that aerosolized coronavirus particles can live up to three hours in the air, meaning they could infect people hours after being expelled.

According to CNN, kissing can transmit the virus and experts say that people who are infected should avoid having sex, since the virus has been found in semen. New research shows that even asymptomatic people, those who have no symptoms of illness, can spread the disease, according to Healthline.