We systematically reviewed the literature to estimate the incubation and latent periods of Ebola virus disease. We found limited epidemiological data from individuals with discrete 1-day exposures. Available data suggest that the incubation and latent periods may differ, and mathematical models may be improved by distinguishing between the two periods.

BackgroundHaemophilus ducreyi and Treponema pallidum subsp. pertenue are major causes of leg ulcers in children in Africa and the Pacific Region. We investigated the presence of DNA (PCR positivity) from these bacteria on asymptomatic people, flies, and household linens in an endemic setting.Methodology/Principal findingsWe performed a cross-sectional study in rural villages of Lihir Island, Papua New Guinea during a yaws elimination campaign. Participants were asymptomatic subjects recruited from households with cases of leg ulcers, and from households without cases of leg ulcers. We rubbed swabs on the intact skin of the leg of asymptomatic individuals, and collected flies and swabs of environmental surfaces. All specimens were tested by PCR for H. ducreyi and T. p. pertenue DNA. Of 78 asymptomatic participants that had an adequate specimen for DNA detection, H. ducreyi-PCR positivity was identified in 16 (21%) and T. p. pertenue-PCR positivity in 1 (1%). In subgroup analyses, H. ducreyi-PCR positivity did not differ in participants exposed or not exposed to a case of H. ducreyi ulcer in the household (24% vs 18%; p = 0.76). Of 17 cultures obtained from asymptomatic participants, 2 (12%) yielded a definitive diagnosis of H. ducreyi, proving skin colonization. Of 10 flies tested, 9 (90%) had H. ducreyi DNA and 5 (50%) had T. p. pertenue DNA. Of 6 bed sheets sampled, 2 (33%) had H. ducreyi DNA and 1 (17%) had T. p. pertenue DNA.Conclusions/SignificanceThis is the first time that H. ducreyi DNA and colonization has been demonstrated on the skin of asymptomatic children and that H. ducreyi DNA and T. p. pertenue DNA has been identified in flies and on fomites. The ubiquity of H. ducreyi in the environment is a contributing factor to the spread of the organism.

Background Treponema pallidum subsp. pertenue causes yaws. Strategies to better control and hopefully eliminate yaws are needed. Methods We conducted an open-label cluster-randomized community trial in a yaws-endemic area of Papua New Guinea. Thirty-eight wards were randomized to receive either one mass drug administration (MDA) round followed by two target treatment of active cases rounds (control arm) or three MDA rounds (experimental arm) at 6-month intervals. The difference in the prevalence of active and latent yaws were measured at 18-month surveys. Results Nineteen wards (30,438 individuals) were randomized to the control arm and 19 (26,238 individuals) to the experimental arm. 24,848 azithromycin doses were administered in the control arm (22,033 at baseline, 207 participants with yaws-like lesions and 2,608 contacts at 6-month and 12-month), compared to 59,852 doses in the experimental arm. At 18 months, the prevalence of active yaws had decreased from 0.46% (102/22,033) to 0.16% (47/29,954) in the control arm and from 0.43% (87/20,331) to 0.04% (10/25,987) in the experimental arm (RR 3.54; 95%CI 1.72–7.27). The prevalence of other infectious ulcers decreased to a similar extent in the two study arms. The prevalence of latent yaws at 18 months, assessed in 994 and 945 children in the control and experimental arms, was 6.54% (5.00–8.08) and 3.28% (2.14–4.42), respectively (RR 2.03; 1.12–3.7). Three cases with resistance to macrolides were found in the experimental arm. Conclusions These data show that three rounds of azithromycin MDA 6 months apart are better than one round of azithromycin MDA with two rounds of targeted treatment for decreasing the community prevalence of yaws. Monitoring for the emergence and spread of antimicrobial resistance is needed. (ClinicalTrials.gov number, NCT03490123.)