Accurate size estimates of key populations (eg, sex workers, people who inject drugs, transgender people, and men who have sex with men) can help to ensure adequate availability of services to prevent or treat HIV infection; inform HIV response planning, target setting, and resource allocation; and provide data for monitoring and evaluating program outcomes and impact. A gold standard method for population size estimation does not exist, but quality of estimates could be improved by using empirical methods, multiple data sources, and sound statistical concepts. To highlight such methods, a special collection of papers in JMIR Public Health and Surveillance has been released under the title "Key Population Size Estimations." We provide a summary of these papers to highlight advances in the use of empirical methods and call attention to persistent gaps in information.

As one of the three West African countries highly affected by the 2014-2015 Ebola virus disease (Ebola) epidemic, Liberia reported approximately 10,000 cases. The Ebola epidemic in Liberia was marked by intense urban transmission, multiple community outbreaks with source cases occurring in patients coming from the urban areas, and outbreaks in health care facilities (HCFs). This report, based on data from routine case investigations and contact tracing, describes efforts to stop the last known chain of Ebola transmission in Liberia. The index patient became ill on December 29, 2014, and the last of 21 associated cases was in a patient admitted into an Ebola treatment unit (ETU) on February 18, 2015. The chain of transmission was stopped because of early detection of new cases; identification, monitoring, and support of contacts in acceptable settings; effective triage within the health care system; and rapid isolation of symptomatic contacts. In addition, a "sector" approach, which divided Montserrado County into geographic units, facilitated the ability of response teams to rapidly respond to community needs. In the final stages of the outbreak, intensive coordination among partners and engagement of community leaders were needed to stop transmission in densely populated Montserrado County. A companion report describes the efforts to enhance infection prevention and control efforts in HCFs. After February 19, no additional clusters of Ebola cases have been detected in Liberia. On May 9, the World Health Organization declared the end of the Ebola outbreak in Liberia.

OBJECTIVE: To determine factors associated with HIV status unawareness and assess HIV prevention knowledge and condom use among people living with HIV/AIDS (PLHIV) in Mozambique. DESIGN: Cross-sectional household-based nationally representative AIDS Indicator Survey. METHODS: Analyses focused on HIV-infected adults and were weighted for the complex sampling design. We identified PLHIV who had never been tested for HIV or received their test results prior to this survey. Logistic regression was used to assess factors associated with HIV status unawareness. RESULTS: Of persons with positive HIV test results (N = 1182), 61% (95% confidence interval [CI] 57-65%) were unaware of their serostatus. Men had twice the odds of being unaware of their serostatus compared with women [adjusted odds ratio (aOR) 2.05, CI 1.40-2.98]. PLHIV in the poorest wealth quintile were most likely to be unaware of their serostatus (aOR 3.15, CI 1.09-9.12) compared to those in the middle wealth quintile. Most PLHIV (83%, CI 79-87%) reported not using a condom during their last sexual intercourse, and PLHIV who reported not using a condom during their last sexual intercourse were more likely to be unaware of their serostatus (aOR 2.32, CI 1.57-3.43) than those who used a condom. CONCLUSIONS: Knowledge of HIV-positive status is associated with more frequent condom use in Mozambique. However, most HIV-infected persons are unaware of their serostatus, with men and persons in the poorest wealth quintile being more likely to be unaware. These findings support calls for expanded HIV testing, especially among groups less likely to be aware of their HIV status and key populations at higher risk for infection.