In some severe COVID-19 cases, the immune system spirals out of control, unleashing a damaging overreaction that worsens patients' conditions. This complex phenomenon leaves clinicians searching for effective interventions.
For roughly 80% of patients, COVID-19 presents with mild to moderate symptoms like fever, fatigue, or a dry cough. The other 20%, however, face a severe form, developing pneumonia accompanied by respiratory failure. Triggered by the virus, the body deploys immune cells to the lungs to combat the infection and repair damaged tissue.
Key players among these defenders are cytokines—signaling molecules that coordinate the immune response. Under normal circumstances, this inflammation is targeted precisely to infected areas. Yet, with a highly virulent virus like SARS-CoV-2, the body can overproduce cytokines, escalating the response beyond necessity.
In such cases, these immune "soldiers" ravage healthy tissue alongside the infected sites. "Instead of aiming at a target with a rifle, it's like using a missile," explains Angela Rasmussen, a virologist and associate research scientist at Columbia University's Mailman School of Public Health, in an interview with National Geographic. This immune overreaction can critically aggravate patient outcomes.
Known as a "cytokine storm," "thunderstorm," or "shock," this has been documented in severe COVID-19 cases and featured in a March 16 study published in The Lancet.
While the exact role of these storms in fatalities remains under investigation, Stanley Perlman, an immunology expert at the University of Iowa with extensive research on SARS and MERS, suggests this hyperactive response "is what really kills patients."
The goal is to dampen these lung "storms" without compromising overall immunity—striking a delicate balance. No proven therapy exists yet, but promising strategies are in urgent trials amid the pandemic.
In Paris, for instance, the AP-HP public hospital network is evaluating anti-inflammatory molecules through its Corimmuno trial.
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