May 28, 2013
H7N9 Virus Found Resistant To Tamiflu Antiviral Medicine
Lawrence LeBlond for redOrbit.com - Your Universe Online
Last week the United Nations reported that the 2013 H7N9 bird flu outbreak was under control in China, stating that closures of live poultry markets likely helped in the decline of cases seen since the beginning of May. The report was welcoming news for a disease that has infected more than 130 people and killed at least 36 since first being detected at the end of March.
But now, on a darker note, a newly released paper is suggesting that an antiviral drug used to treat bird flu patients may not be as effective as health officials had hoped, leaving the door open for further illness and possible death. Publishing the paper in The Lancet, the researchers found that the H7N9 virus has become resistant in three out of 14 patients treated with Roche´s Tamiflu at Shanghai Public Health Clinical Centre.
The resistance was discovered after a gene mutation known to make flu viruses resistant was identified in two patients infected with the 2013 H7N9 flu strain, according to the study. The gene mutation was first discovered in two patients who became the most severely ill out of 14 treated with Tamiflu. The third case of resistance was only spotted after the patient developed the initial infection, suggesting to the report authors that treatment with antivirals may have brought on the mutation.
Tamiflu, which is given in pill form, belongs to a class of medicines known as neuraminidase inhibitors. This class of drug is the only known treatment option for patients with bird flu. Relenza, an inhaled antiviral developed by GlaxoSmithKline, offers the same mode of action.
"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 the paper.
This is the first official confirmation of resistance to Tamiflu, said the researchers. In the other 11 patients treated with the antiviral drug, throat swabs showed a significant reduction in the amount of virus found, leading to a speedy recovery, according to Zhenghong Yuan of Fudan University, one of the researchers conducting the clinical trials.
“Rates of Tamiflu resistance remain low globally, although Roche takes the issue of resistance very seriously and collaborates with international organizations and authorities to monitor the situation,” Silvia Dobry, a spokeswoman for the Switzerland-based Roche, said in an e-mail to Bloomberg.
The World Health Organization said in an earlier report that there have been no new cases of bird flu in China since about May 8, but it is continuing to monitor the situation closely.
Studies into the cause of the virus have established it had been transmitted from birds — most likely chickens — to people. But experts have yet to identify the “reservoir” source of the circulating virus that has led to chickens contracting it and periodically passing it on to humans, reports Reuters.
Juan Lubroth, chief veterinary officer at the UN´s Food and Agriculture Organization (FAO), said last week that the “economic impacts of H7N9 have been astounding.”
“Over $6.5 billion has been lost in the agriculture sector because of prices, consumer confidence and trade. So poultry industry losses in China have been high,” she said, citing information released by China´s Agriculture Ministry.