Prognosis
Patients may experience prolonged virus replication and viral shedding, especially if they are immunosuppressed, and their hospital course may last up to 3 weeks or longer after disease onset.
Between February 2013 and March 2023, approximately 39% of patients with confirmed Asian lineage A(H7N9) virus infection have died.[44] The proportion of fatalities has been similar for each of the epidemic waves. Severity-of-illness data from the second wave revealed that 218 of 219 patients who attended medical services required admission to the hospital and 191 (87.6%) of 218 hospitalised patients were reported to have severe respiratory complications or critical illness.[153] Estimates of symptomatic case-fatality risk suggest that Asian lineage A(H7N9) virus infection is more likely to cause death than seasonal influenza A(H1N1)pdm09 virus infection, but is less likely to cause death than highly pathogenic avian influenza A(H5N1) virus infection.[154] Those who had progressive disease generally died from complications of acute respiratory distress syndrome (ARDS) and multi-organ failure.
No studies have assessed the long-term sequelae of Asian lineage A(H7N9) virus infection among survivors. However, long-term sequelae of acute respiratory distress syndrome include neuromuscular weakness, diminished lung function, post-traumatic stress disorder, and cognitive decline in older patients.[155][156] One cohort study of 56 A(H7N9) patients who survived hospitalisation reported that although pulmonary function and chest computed tomography scan findings had improved by 6 months, most patients had persistent abnormalities 2 years after hospital discharge.[157]
Surviving patients may have immunity to subsequent infection by antigenically similar A(H7N9) virus strains, or decreased likelihood of severe illness if reinfected.
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