Measles epidemics of variable lethality in the early 20th century.

Until the mid-20th century, mortality rates were often very high during measles epidemics, particularly among previously isolated populations (e.g., islanders), refugees/internees who were forcibly crowded into camps, and military recruits. Searching for insights regarding measles mortality rates, we reviewed historical records of measles epidemics on the Polynesian island of Rotuma (in 1911), in Boer War concentration camps (in 1900-1902), and in US Army mobilization camps during the First World War (in 1917-1918). Records classified measles deaths by date and clinical causes; by demographic characteristics, family relationships (for Rotuma islanders and Boer camp internees), and prior residences; and by camp (for Boer internees and US Army recruits). During the Rotuman and Boer War epidemics, measles-related mortality rates were high (up to 40%); however, mortality rates differed more than 10-fold across camps/districts, even though conditions were similar. During measles epidemics, most deaths among camp internees/military recruits were due to secondary bacterial pneumonias; in contrast, most deaths among Rotuman islanders were due to gastrointestinal complications. The clinical expressions, courses, and outcomes of measles during first-contact epidemics differ from those during camp epidemics. The degree of isolation from respiratory pathogens other than measles may significantly determine measles-related mortality risk.

Pathogenic responses among young adults during the 1918 influenza pandemic.

Of the unexplained characteristics of the 1918-19 influenza pandemic, the extreme mortality rate among young adults (W-shaped mortality curve) is the foremost. Lack of a coherent explanation of this and other epidemiologic and clinical manifestations of the pandemic contributes to uncertainty in preparing for future pandemics. Contemporaneous records suggest that immunopathologic responses were a critical determinant of the high mortality rate among young adults and other high-risk subgroups. Historical records and findings from laboratory animal studies suggest that persons who were exposed to influenza once before 1918 (e.g., A/H3Nx 1890 pandemic strain) were likely to have dysregulated, pathologic cellular immune responses to infections with the A/H1N1 1918 pandemic strain. The immunopathologic effects transiently increased susceptibility to ultimately lethal secondary bacterial pneumonia. The extreme mortality rate associated with the 1918-19 pandemic is unlikely to recur naturally. However, T-cell-mediated immunopathologic effects should be carefully monitored in developing and using universal influenza vaccines.

High rates of malaria among US military members born in malaria-endemic countries, 2002-2010.

To estimate malaria rates in association with birth country, we analyzed routine surveillance data for US military members. During 2002-2010, rates were 44× higher for those born in western Africa than for those born in the United States. Loss of natural immunity renders persons susceptible when visiting birth countries. Pretravel chemoprophylaxis should be emphasized.

Extreme mortality after first introduction of measles virus to the polynesian island of Rotuma, 1911.

Rotuma is an isolated Polynesian island. In January 1911, most residents of Rotuma (population approximately 2,600) were exposed to measles virus for the first time. The official mortality register documented 491 deaths due to all causes among Rotumans during 1911 (cumulative measles-related mortality: 12.8%); most deaths occurred in April-May and were attributed to measles and its sequelae. Measles-related mortality rates were higher among young children (23.4 per 100 person-years) and young adults (17.1 per 100 person-years) than among adolescents (11.0 per 100 person-years) and older adults (5.6 per 100 person-years); females (16.2 per 100 person-years) died at a higher rate than males (13.2 per 100 person-years). Gastrointestinal complications (75%), not respiratory complications, were the predominant clinical manifestations of fatal measles cases; tuberculosis mortality was unusually high during the year of the epidemic. In 1911, measles-related mortality varied by nearly 3-fold across geographic districts (range, 7.4%-21.6%). The extreme mortality due to measles on Rotuma typifies the experiences of isolated populations after first encounters with measles; it suggests that prior exposures to a narrow range of microbes and genetic homogeneity predispose isolated populations to lethal outcomes when they are first exposed to highly contagious and pathogenic viruses (e.g., measles, influenza).

Mortality risk factors during the 1918-1919 influenza pandemic in the Australian army.

BACKGROUND: Understanding the risk of mortality during the 1918-1919 influenza pandemic could inform preparations for a future pandemic. METHODS: Prospectively collected demographic, hospitalization, and death data from all individuals who served in the Australian Imperial Force from 1914 through 1919 in Europe and the Middle East were abstracted from archived records. Analyses were conducted to determine mortality risk factors. RESULTS: Hospitalization with a respiratory illness during the spring-summer of 1918 protected soldiers from death (odds ratio, 0.37 [95% confidence interval, 0.25-0.53]; P < .001) but not from hospitalization during the fall-winter of 1918-1919. During the fall-winter of 1918-1919, there was a strong inverse relationship between risk of dying of pneumonia-influenza and time in military service. The pneumonia-influenza death rate among men who enlisted in 1918 (6.33 deaths per 100 person-years) was 9 times higher than that among the 1917 enlistment cohort (0.72 deaths per 100 person-years) and >14 times higher than that among the 1916 cohort (0.43 deaths per 100 person-years), 1915 cohort (0.29 deaths per 100 person-years), and 1914 cohort (0.28 deaths per 100 person-years). CONCLUSION: There was a strong inverse relationship between length of service in the Australian Imperial Force and mortality risk from pneumonia-influenza during the fall-winter of 1918-1919. The protective effect of increased service likely reflected increased acquired immunity to influenza viruses and endemic bacterial strains that caused secondary pneumonia and most of the deaths during the 1918-1919 influenza pandemic.

Deaths from bacterial pneumonia during 1918-19 influenza pandemic.

Deaths during the 1918-19 influenza pandemic have been attributed to a hypervirulent influenza strain. Hence, preparations for the next pandemic focus almost exclusively on vaccine prevention and antiviral treatment for infections with a novel influenza strain. However, we hypothesize that infections with the pandemic strain generally caused self-limited (rarely fatal) illnesses that enabled colonizing strains of bacteria to produce highly lethal pneumonias. This sequential-infection hypothesis is consistent with characteristics of the 1918-19 pandemic, contemporaneous expert opinion, and current knowledge regarding the pathophysiologic effects of influenza viruses and their interactions with respiratory bacteria. This hypothesis suggests opportunities for prevention and treatment during the next pandemic (e.g., with bacterial vaccines and antimicrobial drugs), particularly if a pandemic strain-specific vaccine is unavailable or inaccessible to isolated, crowded, or medically underserved populations.

Incidence rates of pelvic inflammatory disease diagnoses among Army and Navy recruits potential impacts of Chlamydia screening policies.

BACKGROUND: U.S. Navy policy requires Chlamydia trachomatis screening of all women upon entry to recruit training in conjunction with an educational session, and yearly screening thereafter until age 25. Army policy directs only annual screening of asymptomatic women aged <25. Hence, screening of Army recruits may not occur for up to 12 months following accession. Using routinely collected surveillance data, the rates of outpatient pelvic inflammatory disease (PID) following accession into the Army or Navy were compared to assess the potential implications of these policies. METHODS: The population at risk comprised active-component women aged <25 who accessioned to either the U.S. Army or Navy between January 1, 2001, and December 31, 2005. Subjects were followed up to 60 months from accession, either until a first outpatient PID diagnosis occurred or they departed from military service. Data were collected from 2001 to 2006 and analyzed in 2007. Multiple Poisson regression was used to assess the effects of potentially important covariates. Time-to-event analysis was employed to characterize risk over time. RESULTS: There were 1276 and 546 incident outpatient diagnoses of PID among 58,088 Army and 33,046 Navy accessions during 93,918 and 65,863 person-years of follow-up, respectively. The crude incident rate was 64% higher in the Army (13.6/1000 person-years) than the Navy (8.3/1000 person-years). Risk for the Army increased soon after accession, followed by a decline, while risk for the Navy remained comparatively uniform. CONCLUSIONS: PID rates were higher in the Army than Navy during the first years of active service. A comprehensive study to elucidate the source of this observed difference is warranted.

The unusually diverse mortality patterns in the Pacific region during the 1918-21 influenza pandemic: reflections at the pandemic's centenary.

The 1918-21 influenza pandemic was the most lethal natural event in recent history. In the Pacific region, the pandemic's effects varied greatly across different populations and settings. In this region, the pandemic's lethal effects extended over 3 years, from November, 1918, in New Zealand to as late as July, 1921, in New Caledonia. Although a single virus strain probably affected all the islands, mortality varied from less than 0·1% in Tasmania, to 22% in Western Samoa. The varied expressions of the pandemic across the islands reflected the nature and timing of past influenza epidemics, degrees of social isolation, ethnicity and sex-related effects, and the likelihood of exposures to pathogenic respiratory bacteria during influenza illnesses. The high case-fatality rate associated with this pandemic seems unlikely to recur in future influenza pandemics; however, understanding the critical determinants of the mass mortality associated with the 1918-21 pandemic is essential to prepare for future pandemics.

Malaria in U.S. military forces: a description of deployment exposures from 2003 through 2005.

U.S. service members are often deployed to regions endemic for malaria. Preventive measures play an important role in mitigating the risk of disease and adverse effects on mission performance. Currently, a large contingent of U.S. forces is deployed in malarious regions in southeast and southwest Asia. The purpose of this study was to describe malaria cases reported by the tri-service reportable medical events system in terms of exposure (deployment history) and latency of infection. We conducted a retrospective analysis of population health data routinely collected for disease surveillance. All malaria reports received into the Defense Medical Surveillance System by January 3, 2006 with a date of onset between January 1, 2000 and December 31, 2005 in which the individual diagnosed is a member of the active or reserve military components linked to personnel and deployment data were analyzed to determine assignment and deployment history. The main outcome measure was the ICD9-CM diagnosis of malaria (Plasmodium vivax, P. falciparum, P. ovale, P. malaria, and unspecified malaria) by date of onset and days from exposure. A total of 423 cases of malaria were reported during the study period. The Army (n = 325) and the Marine Corps (n = 46) had the highest number of reported cases. Plasmodium vivax (n = 242) and P. falciparum (n = 92) caused nearly four-fifths of all reported cases. During the period from 2003 through 2005, 34% of deployed cases were exposed to more than one malaria-endemic region. Seventy-four cases had been assigned in the Republic of Korea, and all were present in Korea during the high risk transmission period. Seventy-eight cases had documented service in Afghanistan; only 4 had off-season exposure and no other documented exposures. Sixty cases had documented exposure during Operation Iraqi Freedom (OIF). Only six seasonally exposed and six off seasonally exposed OIF cases had no other documented exposure. Fifty percent of Korean cases were diagnosed during an exposure season, and only 3% of Afghan cases were diagnosed during an exposure season. Soldiers in today's military can be exposed to more than one malaria-endemic region prior to diagnosis. This presents new complexities for disease monitoring and prevention policy development.

Incidence rates of malignant melanoma in relation to years of military service, overall and in selected military occupational groups, active component, U.S. Armed Forces, 2001-2015.

During the 15-year surveillance period, there were 2,233 incident diagnoses of malignant melanoma among members of the active component of the U.S. military (unadjusted incidence rate 1.08 cases per 10,000 person-years [p-yrs]). Unadjusted incidence rates were highest in the fi xed-wing pilot/ crew group (2.45 per 10,000 p-yrs); lowest in the infantry, special operations, combat engineer group (0.77 per 10,000 p-yrs); and intermediate among healthcare providers (1.33 per 10,000 p-yrs) and all others (1.07 per 10,000 p-yrs). During the 15-year period, rates of malignant melanoma diagnoses among U.S. military members overall increased in an exponential fashion in relation to years of active service. However, this relationship varied across occupational groups. Most notably, after several years of service, rates of melanoma diagnoses increased relatively rapidly among pilots and the crews of fixed-wing aircraft (e.g., fighters, bombers, cargo/personnel transporters) and those in occupations inherently conducted outdoors (e.g., infantry, special operations, combat engineers). In contrast, melanoma diagnosis rates increased relatively slowly among healthcare providers and those in "other" military occupations. The findings reiterate the importance of limiting, to the extent possible given mission requirements, exposures of military members to solar ultraviolet and cosmic ionizing radiation.

Interactions between influenza and bacterial respiratory pathogens: implications for pandemic preparedness.

It is commonly believed that the clinical and epidemiological characteristics of the next influenza pandemic will mimic those of the 1918 pandemic. Determinative beliefs regarding the 1918 pandemic include that infections were expressed as primary viral pneumonias and/or acute respiratory distress syndrome, that pandemic-related deaths were the end states of the natural progression of disease caused by the pandemic strain, and that bacterial superinfections caused relatively fewer deaths in 1918 than in subsequent pandemics. In turn, response plans are focused on developing and/or increasing inventories of a strain-specific vaccine, antivirals, intensive care beds, mechanical ventilators, and so on. Yet, there is strong and consistent evidence of epidemiologically and clinically important interactions between influenza and secondary bacterial respiratory pathogens, including during the 1918 pandemic. Countermeasures (eg, vaccination against pneumococcal and meningococcal disease before a pandemic; mass uses of antibiotic(s) with broad spectrums of activity against common bacterial respiratory pathogens during local epidemics) designed to prevent or mitigate the effects of influenza-bacterial interactions should be major focuses of pandemic-related research, prevention, and response planning.

Cases and deaths during influenza pandemics in the United States.

OBJECTIVE: To assess how numbers and age distributions of cases and deaths during an influenza pandemic in the United States would potentially vary from those during the 1918-1919 pandemic, given the same virulence of the pandemic strain. METHODS: Influenza cases and deaths in two referent populations (U.S. residents in 1917 and 2006) were calculated using clinical case rates from three pandemics (1918-like, 1957-like, and 1968-like) and case fatality rates from the 1918-1919 pandemic. RESULTS: Across pandemic scenarios, overall case ("attack") rates ranged from 24.7% to 34.2%, and overall death rates ranged from 4.4 to 6.7 per 1000. In both referent populations, total cases and deaths were significantly higher when using 1957-like and 1968-like, compared to 1918-like, case rates. Under all pandemic scenarios, the most deaths occurred among those aged 25 to 29 years. However, in the 2006 referent population, there were large numbers and high proportions of deaths in middle-aged and elderly adults (unlike during the 1918-1919 pandemic). CONCLUSIONS: Numbers and distributions of cases and deaths during influenza pandemics depend on numbers of individuals, clinical case rates, and case fatality rates in relation to age. During a future pandemic in the United States, influenza deaths will likely not be as sharply focused in young adults as in 1918-1919 (even if case fatality rates are similar) because of larger proportions of middle-aged and elderly adults and potentially higher case rates among adults older than 30.

Comparing the population health impacts of medical conditions using routinely collected health care utilization data: nature and sources of variability.

Prevention activities are designed and resourced based on perceptions of the relative population health impacts of various conditions. We examined the nature and variability of rankings of "conditions" based on how they are defined and how their population health impacts are measured. The first listed diagnosis from all hospitalizations and ambulatory visits of U.S. service members during 2002 was used to rank conditions (as defined by two standard classification systems) using five different measures of population health impacts. Less than 10% of all conditions accounted for more than one-half of total population health impact, regardless of how conditions were defined or impacts measured. However, specific conditions with the largest impacts varied depending on the classification system and impact measure. Four groups of related conditions--acute musculoskeletal injuries, pregnancy-related conditions, respiratory infections, and mental disorders (including substance abuse)--accounted for disproportionately large impacts regardless of the measure. The identification of conditions with the largest population health impacts depends on the nature and degree of aggregation in defining conditions and the measure of impact. The findings are relevant to prevention planning and resourcing.

Durations of service until first and recurrent episodes of clinically significant back pain, active component military members: changes among new accessions to service since calendar year 2000.

This report summarizes frequencies and timing of first and recurrent episodes of back pain treated in the U.S. Military Health System among more than 2 million military members who began active service between July 2000 and June 2012. In the population overall, at least 5% were affected by clinically significant back pain within 6 months and 10% within 13 months of beginning active service; and 34% had at least one episode of back pain while in active service during the surveillance period. After initial episodes of back pain, more than half (54%) of those affected had at least one recurrent episode; and after first recurrences, 65% had second recurrences while still in active service. In general, back pain episode-free periods preceding initial and between successive episodes markedly decreased during the period. Frequencies and timing of back pain episodes varied in relation to service branch, gender, and occupation. Acute back pain is a common disorder that is unpredictable in onset and often debilitating. Its prevention should be a military medical research objective of high priority.

Update: Urinary stones, active component, U.S. Armed Forces, 2011-2015.

Urinary stones can cause debilitating morbidity that impairs the operational effectiveness of affected members of the U.S. Armed Forces. This report documents that, during the past 5 years, rates of incident diagnoses of urinary stones decreased by about 17% in the active component of the U.S. military. During the period, annual rates of inpatient diagnosed cases were low and relatively stable, while rates of outpatient diagnosed cases slightly decreased. Incidence rates were slightly higher among females than males in 2011; however, rates were very similar among males and females from 2012 through 2015. Rates of incident diagnoses among white, non-Hispanic and Native American/Alaska Native service members were consistently 80%-100% higher than among black, non-Hispanic and Asian/Pacific Islander service members and 35%-45% higher than among Hispanic and "other race/ethnicity" service members. During the 5-year period, a total of 3,350 service members received more than one incident diagnosis of urinary stones ("recurrent cases"); one-tenth (10.2%) of all incident cases during the period were recurrent cases. Service members with histories of urinary stones should be counseled and closely supervised to avoid dehydration and to adhere to diets that reduce the risk of stone formation.

Variable Mortality From the 1918-1919 Influenza Pandemic During Military Training.

During the 1918-1919 pandemic, influenza mortality widely varied across populations and locations. Records of U.S. military members in mobilization camps (n = 40), military academies, and officer training schools were examined to document differences in influenza experiences during the fall 1918. During the fall-winter 1918-1919, mortality percentages were higher among soldiers in U.S. Army mobilization camps (0.34-4.3%) than among officer trainees (0-1.0%). Susceptibility to infection and clinical expressions of 1918 pandemic influenza varied largely based on host epidemiological characteristics rather than the inherent virulence of the virus.

Durations of military service after diagnoses of HIV-1 infections among active component members of the U.S. Armed Forces, 1990-2013.

This report describes the trends in length of military service for active component members of the U.S. Armed Forces who were diagnosed with human immunodeficiency virus type 1 (HIV-1) infections during 1990-2013. Durations of service after service members' initial diagnoses of HIV-1 infection were compared for five different cohorts that corresponded to when diagnoses were made during the 5-year intervals beginning in 1990, 1995, 2000, and 2005, and the 4-year interval of 2010-2013. By several measures, the durations of service after initial diagnoses of HIV-1 infection increased from the earliest to the later cohorts. The findings are discussed in the context of changes in several factors during the surveillance period: the growing availability and effectiveness of treatments for HIV-1 disease; the stigmas associated with the diagnosis of HIV-1 infection and its link to homosexuality; and the changes in U.S. military policy about the inclusion of homosexuals in its ranks. Also discussed are the limitations of the estimates for the most recent cohorts and the future prospects for continued lengthening of service for those infected with HIV-1.