Johns et al. BMC Public Health 2011, 11(Suppl 2):S3 http://www.biomedcentral.com/1471-2458/11/S2/S3 Page 5 of 9 Figure 2 Epi curve of cases, isolated patients during A/H1N1 outbreak aboard the USS Boxer. Summer 2009. and timing in the pre-deployment process. Sites with large numbers of individuals in the latter stages of pre- deployment were forced to take much more aggressive steps to screen and monitor the symptoms of illness for departing troops. Military service academies were particularly hard hit by novel A/H1N1 outbreaks during the first wave. Nota- ble outbreaks requiring outside assistance and support took place at the U.S. Air Force Academy (USAFA) [17] (Figure 3), U.S. Coast Guard Academy, U.S. Military Academy and U.S. Naval Academy. Response efforts ranged from diagnostic support for cadets and midship- men in isolation to comprehensive outbreak support. The response effort for USAFA was unique because it was the first to provide information on the different aspects of the disease in such a high-risk setting. The USAFA investigation team conducted retrospective and prospective surveillance to describe the epidemiology of the outbreak and to define and implement effective con- trol measures. Extensive education and hygiene efforts were implemented and ill cadets were isolated from non-ill cadets to decrease transmission. The team docu- mented confirmed (n=134) and suspected (n=34) novel influenza A/H1N1 cases among basic cadet trainees, with an outbreak period incidence rate of 11 percent. The peak of the outbreak occurred on July 6 and was likely propagated by a Fourth of July social-mixing event (Figure 4). The investigation team obtained serial nasal wash samples from patients and published the first report of virus shedding duration determined by virus culture. Follow-up nasal wash samples taken seven days from illness onset and from asymptomatic patients (≥24 hours) contained cultureable virus in 24 percent and 19 percent of the samples, respectively. The USAFA investigation made a significant and novel contribution to the general public health knowledge on the transmis- sion dynamics of this disease and demonstrated a high proportion of asymptomatic, sub-clinical disease among cadets in this setting. Remarkably, while notable novel influenza A/H1N1- related outbreaks occurred at all of the basic military training centers, overall, military recruits were only minimally affected during the first wave of the pandemic (Figure 5). Subsequently, the burden of disease shifted almost entirely to recruits at these installations in early fall (August-October) 2009, although the disease burden of novel influenza A/H1N1 among recruits during the entire time was significantly smaller than the ongoing epidemic of adenovirus respiratory diseases among U.S. military recruits [18]. In addition to the novel influenza A/H1N1 outbreaks, four seasonal influenza outbreak investigations were undertaken: one among deployed U.S. troops in Djibouti, one in a refugee camp in Nepal, one onboard a U.S. Navy submarine, and one among newly arrived Japanese military trainees in Camp Pendleton, California. Two H5N1-related investigations occurred, along with an ongoing investigation of human H5N1 cases in Egypt and assistance with human testing during an outbreak of influ- enza in birds in Nepal in November of 2008. Additionally, two respiratory illness outbreak investigations occurred among basic military trainees, while the U.S. Army Public