Public Release: 

Embargoed news from Annals of Internal Medicine

Annals of Internal Medicine tip sheet for August 4, 2009, issue

American College of Physicians

1. Extended-duration Prophylactic Antivirals Effective at Preventing Flu Symptoms

As of early July, the ongoing H1N1 pandemic had caused 94,512 verified infections and 429 confirmed deaths in 122 countries. Experts fear those numbers will rise significantly as H1N1 rapidly spreads during the summer months and into the fall flu season. Current strategies for preventing seasonal and pandemic flu include vaccination and prophylactic administration of antiviral medications. However, vaccinations face several challenges, including a projected four to six month delay to availability. With this in mind, experts look to prophylactic treatment with neuraminidase inhibitors (NAIs) as a potential flu prevention strategy. Researchers reviewed all published randomized, controlled trials of prophylactic administration of NAIs for durations longer than four weeks to develop the best estimates of their safety and efficacy to prevent seasonal flu. They also compared the relative efficacy of two commonly prescribed NAIs, zanamivir and oseltamivir. The researchers concluded that among adults, extended-duration prophylactic treatment with NAIs was effective in preventing symptomatic, but not asymptomatic flu. They found no significant difference in efficacy between oseltamivir and zanamivir.


2. Washing Hands and Wearing Face Masks at Home May Help to Prevent Pandemic Flu

The recent H1N1 pandemic has highlighted the importance of identifying public health measures which can help to mitigate flu virus transmission. Researchers conducted a prospective cluster-randomized trial to test whether improved hand hygiene or surgical face masks could reduce the spread of flu within households. The researchers studied 407 people with flu-like symptoms who visited one of 45 outpatient clinics across Hong Kong within 48 hours of symptom onset, had rapid tests that confirmed infection with influenza A or B, and lived in a household with at least two other individuals, none of whom had reported flu symptoms in the preceding 14 days. The flu patients plus their household members were randomly assigned to one of three groups: control, control plus enhanced hand hygiene, and control plus enhanced hand hygiene plus face masks. The researchers found that hand hygiene and face masks appeared to be effective at preventing household transmission of the flu virus only when implemented within 36 hours of symptom onset. These findings have important public health implications, as they suggest that non-pharmaceutical interventions can reduce flu transmission if implemented early after symptom onset.


ARTICLE:

1. Common Clinical Misconceptions Lead to Misdiagnosis of Clostridium Difficile Infection

The frequency and severity of infection with Clostridium difficile infection are inceasing,and so is resistance to metronidazole treatment. Because of the changing characteristics of the disease, accurate diagnosis is critical. The study authors believe that common misconceptions about the presentation and optimal testing of this infection lead to misdiagnosis of C. difficile infection. The authors conclude that clinicians should give more weight to the patient's clinical presentation and understand that patients who have had less than three loose stools in a day are not likely to have C. difficile infection. When considering testing for C. difficile, clinicians should use a highly sensitive test that identifies toxin B in the stool or pseudomembranes in the colon. If a second test on the same patient is required, the clinician should use a different type of test. Following these principles should reduce misdiagnosis of this infection.

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