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School of Medicine
December 2, 2009- Flu experts at The Johns Hopkins Hospital have received confirmation from the U.S. Centers for Disease Control and Prevention (CDC) and the Maryland Department of Health and Mental Hygiene (DHMH) 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 reported 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.
Infectious disease specialist Trish Perl, M.D., says 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 says is “a serious cause for concern” is that 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 points out, are higher doses of oseltamivir on its own or with other antiviral medications, including zanamivir (Relenza) or oseltamivir and the antiviral rimantadine (Flumadine).
Perl, senior hospital epidemiologist responsible for infection control at Johns Hopkins, says 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,” says Perl, a professor of medicine and pathology at the Johns Hopkins University School of Medicine.
As a precaution, the families of both men have been vaccinated against H1N1 as well as seasonal flu.
According to internist Redonda Miller, M.D., M.B.A., Johns Hopkins vice president for medical affairs and the hospital’s chief patient safety officer, neither infected patient, 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 inpatient had a separate, private room and wore masks whenever they left the room, even for walks down the hall. In addition, says Miller, all staff working with such patients were vaccinated against H1N1 and were required to wear masks.
“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,” says respected infectious disease specialist John Bartlett, M.D.
“Oseltamivir resistance is still very rare,” he says, 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,” adds Bartlett, who was director of infectious diseases at Johns Hopkins for more than 25 years.
– JHM –
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Media contact: David March