Baloxavir alleviates severe disease and viremia in ferrets infected with avian- or bovine-origin influenza A(H5N1) virus

Influenza A(H5N1) viruses have expanded globally among wild birds, poultry, and mammals, most recently in North American dairy cattle. Humans exposed to infected animals may also become infected, with potential for severe disease outcomes. In this work, Jones et al. treated severe A(H5N1) disease in a ferret model using the drug baloxavir. One to three doses of baloxavir before or after virus inoculation improved survival (50 to 100%), morbidity, and clinical illness in infected ferrets. Treatment lowered viral shedding, lung injury, viremia, and spread of the virus to the brain. Multidose drug regimens provided the best results overall. Resistance of virus to baloxavir was found to be rare, but monitoring viral samples from treated patients with A(H5N1) is still necessary.