COVID-19 & the immune system

Find out about the relationship between the two & why the virus can affect people in different ways

Coronavirus (COVID-19) is an illness caused by a newly discovered coronavirus (SARS-CoV-2), that can affect the lungs and airways. We’re all familiar with the things we need to be doing to help prevent catching and spreading the virus. But what do we know about what it does to our bodies and how our immune system fights back if we do catch it? Let’s find out the facts.

What happens to the body during a COVID-19 infection?

Sars-CoV-2 can enter the body if you breathe it in (after someone who’s infected coughs, breathes or sneezes near you) or if you touch a contaminated surface and then your face. The virus infects the cells that line your throat, airways and lungs. By infecting these cells, it can make copies of itself. These copies can then infect more cells. The immune system works hard to stop this, to prevent the virus spreading throughout the body.

There are two main parts to the immune system. The first is the innate immune system which acts as the first line of defence on the battlefield. We’re born with it, it’s fast acting and non-specific which means it targets and destroys anything it sees as harmful. If a virus escapes this system, then the second line of defence (the adaptive immune response) kicks in. Constantly learning as we go through life, it’s able to remember and recognise anything that it’s come in contact with in the past. Because Sars-CoV-2 is a new virus, scientists are still learning about the exact way that it interacts with the immune system.

Why does COVID-19 affect people in different ways?

Most people with coronavirus will have at least one of these symptoms:

• A high temperature

• A new, continuous cough

• A loss or change to your sense of smell or taste

Some people may have no symptoms at all.

In most people, their immune system is strong enough to help them recover from the infection. Unfortunately though for some, this isn’t the case and their condition will get worse which may mean they’ll need to go to hospital. How our immune system responds to a virus such as SARS-CoV-2 is influenced by lots of things. These include our general health, our age and our genes. While it’s possible for COVID-19 to make anyone seriously ill, for some the risk is higher. Those at a greater risk include anyone who:

• Has had an organ transplant

• Is having chemotherapy or antibody treatment for cancer

• Is 70 or older

• Has a lung condition

• Has a condition that means they have a very high risk of getting infections

• Has had a bone marrow or stem cell transplant in the past six months, or is still taking immunosuppressant medicine

• Has heart disease (such as heart failure)

• Has diabetes

• Is taking medicine that can affect the immune system (such as low doses of steroids)

• Is very obese (a BMI of 40 or above)

As COVID-19 is quite a new disease, there’s still limited evidence. Research is ongoing as to why some of these conditions increase the risk of complications.

Are there any long-term effects of COVID-19?

While most people with COVID-19 recover pretty quickly, some have symptoms that can last for weeks or even months. Even people who have mild illness and don’t go to hospital can experience ongoing symptoms. This is a condition that’s now commonly known as Long COVID. The most common long-term symptoms seem to include:

• Fatigue

• Shortness of breath

• Cough

• Joint pain

• Chest pain

As this is a new condition, there’s no definite answer for why the virus may cause Long COVID symptoms (although there are lots of ideas). The best way to protect against Long COVID is to follow the advice to help prevent catching COVID-19 in the first place. This includes following social distancing guidelines, washing your hands regularly and following your government guidelines.

Information correct at time of publication (12.01am 23/12/2020)