MUMBAI: Here is one of the reasons Covid-19 has emerged as a major killer: patients deteriorate quickly and collapse.After attending to over 2,000 patients and witnessing 160 deaths, the state’s experts have prepared a dossier of sorts on the virus and its ‘novel’ manifestations and attacks. It is by now well accepted that 85% to 90% of coronavirus patients have mild to non-existent symptoms (fever, cough or breathlessness). The public health department is worried not only because the virus is new and little is known about it, but the case fatality rate here is highest in the country at 6.85%.The dossier is an effort to list all the novel symptoms. If the virus behaves benignly in 85-90% patients, it’s tricky in the rest. The change in their health parameters could be rapid."Several cases have been seen in Pune where the patient is laughing and talking just before deteriorating and dying in the next few hours,” said Dr Subhash Salunkhe, technical advisor to the state chief secretary. On Monday, deaths and treatment outcomes were a point of discussion in a videoconferencing meet between CM Uddhav Thackeray, the chief secretary, medical heads and doctors.Another official said, “The need for the meeting was felt because we have to firm up our treatment plans. The fact is that a stable patient with oxygen saturation of more than 90% desaturates rapidly and collapses.” It is felt Covid-19 cases behave differently than routine ARDS (acute respiratory distress syndrome) patients who need ventilator support. ARDS or respiratory failure can be caused by many bacteria or viruses, while here it is caused by just one. This subset of Covid-19 patients needs ventilator support.Doctors have also noticed weakened heart and kidney function among this group. An autopsy of six patients showed inflamed heart tissues, said the document.