As the number of cases of the novel coronavirus continues to rise (now up to 125,000 globally ), people have a *lot* of questions about how the virus spreads , and how susceptible they might be. It's most likely to be passed on through human-to-human contact , experts say, which is why many companies are encouraging employees to work from home and businesses are shutting down to help get the spread under control.

But limiting contact with others isnt just for your own benefit. While young adults don't seem to be getting seriously sick from COVID-19, the same can't be said for everyone. The elderly are especially at risk, as well as those who are immunocompromised. (FYI: Elderly individuals are not necessarily immunocompromised, but research has shown that aging impacts the immune system, and older adults may be less able to fend off infection compared to younger, healthy people.)

Also, symptoms of the new coronavirus are slow to show, meaning you might be a carrier for the virus without even knowing it and, in turn, put those who fit into one or both of those high-risk categories in danger if they were to be exposed.

So why exactly are certain groups more at risk, and what does immunocompromised actually mean? Here, , PhD, a microbial and viral infection researcher at Montana State University, explains everything you need to know.

First, who is most at risk for *catching* coronavirus?

Because humans haven't faced the new coronavirus before, no one has a built up an immune response to it. Basically, that means everyone has an equal risk of getting novel coronavirus, though not everyone will have symptoms or be effected by the virus to the same degree.

Those who are immunocompromised aren't at a higher risk of contracting COVID-19, but they are at an increased risk of developing severe symptoms from it, including death.

So what does it mean to be immunocompromised?

Simply put, being immunocompromised (or immunosuppressed) means having a weakened immune system, Loveday says. It means you have a reduced ability to [have] an effective immune response, she says.

Its essentially the opposite of being immunocompetent, or having a normal immune response to protect the body when it feels threatened. Those who are immunocompromised might get sick more often, stay sick longer, and be more vulnerable to different types of infections.

What conditions make you immunocompromised?

People with chronic conditions like hypertension, diabetes, cardiovascular disease, chronic respiratory disease, and cancer are at the highest risk for severe disease and death associated with COVID-19, according to a study by the World Health Organization (WHO) .

Here's a look at just how much greater that risk is: According to a study of 1,590 patients from China, those infected with COVID-19 who were already dealing with a chronic condition were 1.8 times more likely than those with no underlying conditions to have a poor outcome, such as being put on a ventilator or dying. People in the study with two chronic conditions were 2.6 times more likely. Those numbers translated into a poor outcome for nearly 20 percent of the patients who had at least one chronic condition, compared with 4.5 percent of those without any chronic ailments.

Other conditions that affect the immune systemincluding Crohn's disease , lupus , psoriasis, and arthritiscould also impact the severity of symptoms people experience from the new coronavirus. But their risk of developing severe disease may differ depending on their individual degree of immunosuppression, Loveday explains. For example, HIV/AIDS causes a weakened immune system by reducing the amount of infection-fighting T-cells in the body, but many people with this condition take antiviral meds that boost their immune system to the point where they're no longer at a much higher risk.

On the other hand, people who take steroids or immunosuppressive therapieslike for organ transplant or to treat specific autoimmune diseasesare at a higher risk, since the drugs they take effectively work to reduce the immune response so the organ is not rejected, or to reduce the autoimmune response that leads to disease. Chemotherapy also reduces immune system function.

What are symptoms of coronavirus like for immunocompromised people?

Loveday says the most common symptoms are fever, fatigue, and respiratory symptoms, including a cough, sore throat, and shortness of breath. Symptoms [for the immunocompromised] can last up to 20 or more days, she says. This does not mean everyone will be sick for this long, but some reported cases have lasted upwards of 20 days.

Again, it's unclear exactly how everyone who has a suppressed immune system will respond to the virus. Even though they're at a higher risk of complications, whether or not they develop those severe symptoms is really a case-by-case basis.

What should you do if you think youve been exposed to the coronavirus and youre immunocompromised?

If you think you have been exposed, call your doctor [and explain your symptoms]," says Loveday. "If you end up with shortness of breath, you need to go to the emergency room right away."

Whether or not a person who is immunocompromised develops severe symptoms is really a case-by-case basis.

Clinicians are able to access tests at their discretionbut Loveday warns that you most likely will not get tested unless severe disease is present , meaning youre currently exhibiting shortness of breath and other respiratory distress that would warrant a visit to the ER.

How can you protect yourself if you have a chronic condition or live with someone who does?

The number-one way to protect yourself and those living with you that may be at higher risk for severe disease is to practice social distancing whenever possible, wash your hands often , and avoid touching your face unless you just washed your hands.

She also suggests trying to keep highly used surfaces (e.g., cell phones and door handles) clean using normal sanitizing sprays and cleansers. If you develop symptoms (whether you're immunocompromised or not), you can wear a surgical face mask to help protect others from your cough or sneezes, according to the latest advice from the CDC . (Reminder, though, wearing a surgical mask when you're healthy doesn't help prevent you from catching the virus.) And if you are feeling sick, it's best to stay home as much as possible to prevent spreading germs.

If you share a space with someone who is immunocompromised, dont share food, plates, or utensils with themand unfortunately, hugging and kissing is off-limits. Its also important that higher-risk people and well-fed and make sure theyre getting enough sleep, so their bodies can be better prepared if they come into contact with the virus.