On the other hand, in four outbreaks in Singapore military camps, when NAIs were able to be delivered effectively in conjunction with isolation of confirmed cases and quarantine of contacts, a beneficial effect could be demonstrated. These measures, which included ring prophylaxis with oseltamivir, resulted in a reduction of the infection rate in the outbreaks from 6.4% to 0.6% [40] . This study demonstrates the potential benefit of NAIs if available early in outbreaks, and when combined with social distancing. However extension of this strategy to large heterogeneous populations remains unproven and it may be feasible only in closed communities, such as boarding schools, military barracks and residential care facilities.