In a study of 11 patients in Shanghai, Chinese doctors found that two samples of the virus have developed a mutation that makes them resistant to the drug — meaning the treatment was rendered ineffective.
In one patient, they even saw the resistance take hold after initial infection. The virus adapted to treatment with the drug while it was infecting the patient’s body. After nine days of treatment with the drug, the virus developed a mutation in the neuraminidase gene, the N in H7N9. This mutation made the drug ineffective.
The patients with the mutation were the ones who did the worst after getting to the hospital — they ended up on breathing machines and on machines that oxygenated their blood outside of their body, called ECMO. One died.
“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,” the researchers wrote in an article published online by The Lancet [PDF] medical journal on Tuesday, May 28.
The virus, which seems to come from birds, has infected 133 people and killed 36, according to FluTrackers. There could me more cases lurking out there that haven’t tested positive. Cases have been slowing in recent weeks, but the threat that it could mutate and infect more people remains as long as it’s still circling in animal populations.
NOW WATCH: Briefing videos
Business Insider Emails & Alerts
Site highlights each day to your inbox.