For the latest study, researchers followed 14 H7N9 patients admitted to the Shanghai Public Health Clinical Centre in China between April 4 and 20.
All had been given antiviral treatment, either oseltamivir or peramivir, and 11 showed a drop in viral count.
Three, however, had a "persistently high viral load" in spite of treatment and had to be placed on respiratory support machines.
Two of them died, said the study authors.
From The Lancet:
May 28, 2013
Association between adverse clinical outcome in human disease caused by novel influenza A H7N9 virus and sustained viral shedding and emergence of antiviral resistance
Summary Background On March 30, a novel influenza A subtype H7N9 virus (A/H7N9) was detected in patients with severe respiratory disease in eastern China. Virological factors associated with a poor clinical outcome for this virus remain unclear. We quantified the viral load and analysed antiviral resistance mutations in specimens from patients with A/H7N9
In conclusion, oseltamivir treatment, even when started 48 h or more after disease onset, was associated with falling viral load in the respiratory tract in most patients with A/H7N9 infection. Therefore, early treat - ment of suspected or confirmed cases is strongly encouraged. The emergence of an NA Arg292Lys mutation in two patients infected with A/H7N9 was temporally associated with a rebound of virus load, treatment failure, and a poor clinical outcome. The role of cortico steroids in facilitating the emergence of the NA Arg292Lys mutation or even directly affecting viral load and adverse clinical outcome deserves consideration. The fitness and stability of the Arg292Lys mutation in A/H7N9 needs to be investigated. The apparent ease with which antiviral resistance emerges in A/H7N9 viruses is concerning; it needs to be closely monitored and considered in future pandemic response plans.