December 7, 2009
First reported cases of Tamiflu-resistant H1N1 treated at JHH
Flu experts at The Johns Hopkins Hospital have received confirmation from the U.S. Centers for Disease Control and Prevention and the Maryland Department of Health and Mental Hygiene that two recently treated patients with 2009 H1N1 flu, both since discharged, had drug-resistant forms of the virus.
Laboratory tests performed at the CDC and DHMH showed that both cases had type A strains of the latest influenza virus resistant to the drug oseltamivir, better known as Tamiflu, the initially recommended and most widely used drug treatment available. These cases are believed to be the first two cases of drug-resistant H1N1 infection reported in Maryland. The World Health Organization has reported at least 57 cases worldwide of oseltamivir resistance in people infected with novel H1N1, with more than 20 in the United States, including a cluster of four recently reported cases in North Carolina.
Trish Perl, senior hospital epidemiologist responsible for infection control at Johns Hopkins, said that the emergence of such mutations is “not surprising” as viruses mutate naturally as they infect more and more people, and even more so when an antiviral is in widespread use. But what she said is “a serious cause for concern” is that a widespread emergence of oseltamivir-resistant strains would severely curtail the number of drugs available to treat the disease, especially if the virus mutates into a more contagious or more virulent form. Current treatment options, she pointed out, are taking higher doses of oseltamivir, switching to zanamivir (Relenza) or using oseltamivir in combination with rimantadine (Flumadine), another antiviral drug.
Perl says that vaccination is the best defense against new and potentially more dangerous strains of H1N1. “If you are vaccinated against H1N1, you are protected against catching the virus. Everyone should get vaccinated,” said Perl, a professor of medicine and pathology at the Johns Hopkins School of Medicine.
As a precaution, the families of both men treated at the hospital have been vaccinated against H1N1 as well as seasonal flu.
According to internist Redonda Miller, vice president for medical affairs and the hospital’s chief patient safety officer, neither of the infected patients, both of whom had weakened immune systems, was at serious risk of transmitting the drug-resistant strain to other people in the hospital as each had a private room and wore a mask when leaving his room. In addition, Miller said, all staff working with such patients were vaccinated against H1N1 and are required to wear masks.
Infectious disease expert John Bartlett, a professor in the School of Medicine, said, “The lesson from these drug-resistant cases is that all physicians and health care workers in Maryland really need to be vigilant in their monitoring of H1N1 and in getting people who are prioritized as at high risk for infection vaccinated for both seasonal flu and H1N1.”
Oseltamivir resistance is still very rare, he said, noting that it occurs in less than 1 percent of all cases of 2009 H1N1 infection and, in nearly all cases, in people who have previously taken the medication.
“In order to minimize widespread resistance, physicians also need to focus their use of oseltamivir, as set out in CDC guidelines, on those patients with H1N1 who are at highest risk of complications from the infection and seriously ill enough to require hospitalization,” added Bartlett, who was director of Infectious Diseases at Johns Hopkins for more than 25 years.