Written by:
Ioannis Psallidas
Global Clinical Head, Late R&I, AstraZeneca
Lung infections caused by respiratory viruses are common and we’ve all had them at some time or another. Yet, in a small number of cases, they develop into a more serious condition, called acute respiratory distress syndrome (ARDS)1, which requires hospital treatment. People with ARDS have extensive lung damage and are typically admitted to intensive care so that a ventilator can help with their breathing. Many cases of ARDS are caused by the body’s immune system overreacting to the original infection. Treatments that address this overactivity could save lives and help to restore lung function.
The impacts of ARDS
As someone with a severe viral respiratory infection progresses towards ARDS, they will experience increasingly significant negative impact on their health. This includes increased symptom severity, mortality and risk of developing additional illnesses. These people typically need much more healthcare support, which can mean much more time in hospital, more invasive procedures, longer recovery times and greater costs.
A systematic research review included almost 11,000 people, largely from China, Spain and France, who had ARDS resulting from viral respiratory infections caused by COVID-19. The results showed that around 40% died, largely as a result of sepsis and/or multi-organ failure1.
Emerging evidence suggests that timely intervention is crucial to managing the severe effects of viral respiratory infections on the immune system to reduce cases of ARDS and ensure more positive outcomes for patients.
Learn from our scientific leaders about our work on respiratory virus infections
The immune system and respiratory viruses
The immune system is key to defending our bodies from infections and other illnesses. It has many ways to attack and destroy cells, viruses and other causes of illness. But this means the immune system needs to be carefully controlled, so that it only responds to harm and doesn’t start to damage healthy cells.
When a pathogen such as a virus activates the immune system, it becomes very easy for the immune system to become hyperactive and cause harm. These infections can be caused by many viruses but some of the most common ones include influenza, novel corona viruses and respiratory syncytial (RSV). People develop ARDS when their immune system damages the lungs so much that they are unable to function effectively. ARDS often develops rapidly and can be associated with a dramatic deterioration in health. Signs of ARDS include inflammation and excess fluids in the lungs which make them less efficient at exchanging gases between the air we breathe and the blood.
Find out how viral respiratory infections lead to over activation of the immune system and ARDS.
All our cells need oxygen to survive. Ventilation can help get more oxygen into the blood if the lungs are damaged but there are risks and limitations, especially if the lungs become too damaged it is impossible to get enough oxygen to the organ.
Underlying disease drivers in viral respiratory infections
One of the key proteins involved in progression to ARDS associated with viral infections is called IL-33. Viruses cause illness by entering and replicating inside our cells and then destroying the cells when they break out of them. These cells release IL-33, which perpetuates its activity during ARDS in activating the immune system.
By suppressing the overactive immune system we believe it could be possible to limit or reverse damage to the lungs while using other treatments, such as antivirals, to cure the infections. This could have the potential to reduce the number of severe cases resulting from viral and other infections, meaning less need for intensive care and a faster return to living a normal life.
