Question

What is a ‘cytokine storm’? I keep reading about this in relation to COVID-19. Is it related to the cytokine abnormalities that have been found in ME/CFS? And could it help to explain why some people are developing Long COVID, which seems to have very similar symptoms to ME/CFS.

Answer

A ‘cytokine storm' results from a sudden acute increase in circulating levels of different pro-inflammatory cytokines. Cytokines are immune-system chemicals that are released to help coordinate the body’s response to an infection and they trigger inflammation. Sometimes this response goes into overdrive with an excessive production of cytokines. In the case of a Covid-19 infection, the virus enters the lungs where it causes localised inflammation. In some cases, if a cytokine storm results, it can cause serious lung damage, or even be fatal.

Cytokine storms are a common complication not only in Covid-19 and influenza (Flu) but of other respiratory diseases caused by coronaviruses such as SARS and MERS. They can also be associated with non-infectious diseases such as multiple sclerosis and pancreatitis. Cytokine storms might help explain why some people have a severe respiratory reaction to Covid-19 while others only experience mild symptoms. And they could be the reason why younger people are less affected, as their immune systems are less developed and so produce lower levels of inflammation-driving cytokines.

As you correctly point out, there is growing research evidence in ME/ CFS to indicate that the cytokine response that occurs during the acute stage of any infection fails to settle down. As a result, there is on-going low-level immune system activation. This could then result in the on-going ‘flu-like' symptoms that many of us experience. The same reasoning could help to explain what is happening in Long Covid. We may know more about this when research studies looking at what happens to the immune system from the onset of a Covid-19 infection start to appear.

More information

• The ME Association has been producing free information about Covid-19, vaccinations, Long Covid, and ME/CFS since the start of the pandemic. Visit the website shop to download.
• See: National Geographic: Two years later, coronavirus evolution still surprises experts. Here’s why. | Sub-heading: Not just a respiratory virus. | 11 March 2022.