Severe symptoms are mainly due to hyperactivation of the immune response and cytokine shock; the stronger the immune response, the more severe the lung damage.
Dalili kali mara nyingi hutokana na kuchochewa sana na kinga ya mwili kupigana kupita kiasi na mlipuko wa saitokini ambapo kinga ya mwili likiwa thabiti sana, mapafu huharibika zaidi.