Various coronaviruses can cause respiratory infections in humans, from your average cold to more severe illnesses, like Severe Acute Respiratory Syndrome (SARS). COVID-19 is spread mainly by respiratory droplets from people with a cough or other symptoms, such as fever or fatigue, OR people with very few symptoms (especially at the start of the disease).  

It appears that some asymptomatic people can also spread the disease, but how often this occurs is still unknown.  

Though specialists have dealt with coronaviruses for many years, we are only beginning to understand the mechanisms of COVID-19.

A virus is not a cell. It’s a capsule containing genetic material; think of it as a factory without machines. It has to invade our cells, which contain the machines it needs in order to multiply. A certain period of time is required for the virus to multiply inside our bodies before attacking. This is called the incubation period, the time from infection (when the virus spreads to you from another person and enters your body) to the onset of symptoms. COVID-19 generally has an incubation period of three to five days, but it can last up to 14 days.  

People usually only get checked for COVID-19 when they have symptoms, rather than during the incubation period. 

How does the immune system respond to COVID-19? 

The immune system can be compared to an army with various battalions (cells and organs) and weapons (such as antibodies) responsible for defending us against all kinds of attackers.  

There are two types of immune responses: 

• - Innate, or nonspecific, responses (fever, for instance) are the first line of defense against infection. They act in the same way regardless of the type of disease being fought. 
• - Acquired, or specific, responses are triggered by a chain reaction. They produce, among other things, antibodies. 

If you are infected with COVID-19, your body recognizes this intruder as it would any infection, and responds by attacking the virus. Cells in your immune system recognize this agent of infection, send out messages to alert other immune cells, and produce antibodies to neutralize the virus. What makes COVID-19 different is that this immune response, which normally occurs over a short time period, can go into overdrive in some people, causing damage and complications.  

Diseases caused by coronaviruses, such as the common cold, usually end in immunity, meaning you have a trained army in your body ready to attack the same virus again. Currently, there is not evidence to prove that people who have recovered from COVID-19 and have antibodies are protected from a second infection. Some of these people have very low levels of neutralizing antibodies in their blood, suggesting that cellular immunity may also be critical for recovery.  

Our immune system’s response to COVID-19 is still under study. Gaining a better understanding of this response will allow researchers to reproduce it in a vaccine.  

Testing for COVID-19 

Two kinds of tests are available: 

• Viral (nasal) tests tell you if you have the virus at the time of testing.  
• Serology (blood) tests tell you if you have antibodies against the virus, meaning you’ve had COVID-19 already and developed antibodies against it.  

If you go to get tested for COVID-19, you will be administered a viral test. If you test negative, you were likely not infected at the time the nasal test was administered, but that doesn’t mean you won’t get sick.  

Serology tests are used for retroactive diagnoses that may not have been established by viral testing due to a false negative. They are also used to determine whether someone had COVID-19 if no symptoms were reported.  

If you receive a positive result from one of these tests, researchers do not yet know whether you can get COVID-19 a second time, whether you will be protected if you are infected again, or whether you will be able to fight a second infection.

Can I get tested and then visit a loved one with blood cancer?  

Viral tests tell you whether you had the virus at the time of testing. When you get back the results, even if you test negative, you may have been infected since and therefore be at risk of infecting your loved one.  

Serology tests detect antibodies. As antibodies do not develop immediately, there is a significant risk of receiving a false negative at the onset of the disease. Furthermore, even if you test positive, that doesn’t mean you are protected and can’t get infected again, meaning you could put your loved one at risk.  

A person undergoing blood cancer treatment or in remission from a blood cancer may be immunosuppressed.

Because of this, we must protect them by following proper distancing measures. Take precautions if you wish to visit a loved one with a blood cancer.