New Research Shows Resistance to Tamiflu Treatment in Those With H7N9 Virus

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On March 30, 2013, 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. In a new paper appearing in The Lancet, Hu, et al. (2013) quantified the viral load and analyzed antiviral resistance mutations in specimens from patients with A/H7N9.

The researchers studied 14 patients with A/H7N9 disease admitted to the Shanghai Public Health Clinical Centre (SPHCC), China, between April 4, 2013 and April 20, 2013, who were given antiviral treatment (oseltamivir or peramivir) for less than two days before admission. The researchers report that they investigated the viral load in throat, stool, serum, and urine specimens obtained sequentially from these patients; they also sequenced viral RNA from these specimens to study the mutations associated with resistance to neuraminidase inhibitors and their association with disease outcome.

According to the reswearchers, all patients developed pneumonia, seven of them required mechanical ventilation, and three of them further deteriorated to become dependent on extracorporeal membrane oxygenation (ECMO), two of whom died. Antiviral treatment was associated with a reduction of viral load in throat swab specimens in 11 surviving patients.

Hu, et al. (2013) conclude that "Reduction of viral load following antiviral treatment correlated with improved outcome. Emergence of NA Arg292Lys mutation in two patients who also received corticosteroid treatment led to treatment failure and a poor clinical outcome. The emergence of antiviral resistance in A/H7N9 viruses, especially in patients receiving corticosteroid therapy, is concerning, needs to be closely monitored, and considered in pandemic preparedness planning."

Reference: Hu Y, Lu S, Song Z, et al. Association between adverse clinical outcome in human disease caused by novel influenza A H7N9 virus and sustained viral shedding and emergence of antiviral resistance. The Lancet, Early Online Publication, May 29, 2013. doi:10.1016/S0140-6736(13)61125-3

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