Test flu specimen to determine treatment for elderly

The 2009-H1N1 influenza epidemic has mostly affected young people so far, but health professionals should take care to protect the vulnerable elderly from infection, said during an influenza symposium at the annual meeting of the American Geriatrics Society.

Speakers said that the outbreak highlights the need for new drug and vaccines to fight influenza in the elderly.

“You should do general infection control: hand hygiene, cough etiquette, and social distancing. The General party line is 6 feet for social distancing, but the farther the better to avoid transmission.”

Transmission between generations within families has been reported in several countries. Two audience members noted that residents of their New Jersey nursing home had influenza A just one week before the epidemic came to light, and they speculated that they might have witnessed early cases in the swine-origin 2009-H1N1 outbreak.

Nursing homes and other long-term care facilities with active cases of influenza should halt group dining and instead deliver meals to individuals’ rooms, cancel group programs, and restrict staff movement between wards. To protect incoming residents, facilities should delay new admissions to a ward for seven days after a case of influenza has been confirmed there, suggested a professor of medicine at Brown University and clinical director of the company Quality Partners of Rhode Island, both in Providence.

“If you have someone who is sick, keep them in their room. If a facility has no influenza cases, it can continue to operate as usual, except for the usual seasonal influenza precautions.”

The triad of cough, a temperature higher than 38ºC, and illness lasting seven days or less is a reasonably sensitive indicator of contagious influenza, but the gold standard is a viral culture. Viral culture allows for strain typing and resistance testing, both of which are important in the current outbreak. The disadvantage of waiting for an infection to be confirmed by culture is that it can take 3 to 7 days. That delay can impede infection control and lapse beyond when antiviral treatment should begin.

Real-time polymerase chain reaction testing is good but expensive and not yet widely available. Immunofluorescense or enzyme immunoassay can give results within 15-30 minutes, but should be followed with viral culture, if possible.

No matter which test for 2009-H1N1 is used, it’s only as good as the specimen taken, emphasized a professor of medicine, infectious disease, at the University of Rochester (NY) School of Medicine and Dentistry. Samples should be taken using a nasal swab in both nostrils and a separate throat swab, preferably with plastic rather than wooden swabs.

Viral isolation is important because different influenza viruses are susceptible and resistant to different drugs, she said. “Information on antiviral sensitivities of the recently circulating H1N1 influenza is preliminary, but this virus appears to be sensitive to oseltamivir and zanamivir but resistant to the adamantanes, unlike seasonal H1N1 influenza.”

Oseltamivir (Tamiflu) resistance has been a growing concern worldwide. The Centers for Disease Control and Prevention reported oseltamivir resistance in 0.7% of 588 influenza A H1N1 isolates during the 2006-2007 flu season. That number jumped to 12% of 1,026 isolates during the 2007-2008 flu season. And as of Jan. 24, 2009, 98% of H1N1 isolates tested in the United States were resistant to oseltamivir.

Resistance is 16% worldwide. However, oseltamivir resistance does not seem to be associated with previous use of the drug. The prevalence resistant isolates is low in Japan, where the agent is widely used, and resistance is present in low in Japan, where the agent is widely used, and resistance is present in Denmark, where oseltamivir is not used. The most likely explanations for the resistance occurring are point mutations and drift in the virus.

Zanavimir would be the preferred medication for any H1N1 virus, but a combination of oseltamivir and rimantadine could be prescribed. “There has been a little bit of data that combination therapy makes some sense and may reduce resistance.”

Clinicians might also want to use antiviral therapy beyond the 48-hour window after symptom onset, as recommended by the Advisory Committee on Immunization Practices. In one study, antiviral therapy was associated with a significant reduction in mortality even though only 29% of patients were treated within 48 hours.

Influenza vaccines in the elderly are associated with substantial benefits in terms of reduced illness, hospitalization, and death, although there is some controversy about the magnitude of the mortality benefit, said a professor at the University of Minnesota and the Minneapolis VA Medical Center. The controversy derives from concerns about the methodology in observational studies, possible bias in studies of healthy vaccines, and the fact that influenza mortality rates have not declined overall, despite increases in vaccination rates.