Estimating the number of probable new SARS-CoV-2 infections among tested subjects from the number of confirmed cases.

OBJECTIVES: In most African countries, confirmed COVID-19 case counts underestimate the number of new SARS-CoV-2 infection cases. We propose a multiplying factor to approximate the number of biologically probable new infections from the number of confirmed cases. METHODS: Each of the first thousand suspect (or alert) cases recorded in South Kivu (DRC) between 29 March and 29 November 2020 underwent a RT-PCR test and an IgM and IgG serology. A latent class model and a Bayesian inference method were used to estimate (i) the incidence proportion of SARS-CoV-2 infection using RT-PCR and IgM test results, (ii) the prevalence using RT-PCR, IgM and IgG test results; and, (iii) the multiplying factor (ratio of the incidence proportion on the proportion of confirmed -RT-PCR+- cases). RESULTS: Among 933 alert cases with complete data, 218 (23%) were RT-PCR+; 434 (47%) IgM+; 464 (~ 50%) RT-PCR+, IgM+, or both; and 647 (69%) either IgG + or IgM+. The incidence proportion of SARS-CoV-2 infection was estimated at 58% (95% credibility interval: 51.8-64), its prevalence at 72.83% (65.68-77.89), and the multiplying factor at 2.42 (1.95-3.01). CONCLUSIONS: In monitoring the pandemic dynamics, the number of biologically probable cases is also useful. The multiplying factor helps approximating it.

[Snakebites in the Sudanian and Sahelian zones of Mali: epidemiology, symptoms and treatment]. / Morsures de serpents en zone soudano-sahélienne du Mali epidémiologie, symptomatologie et traitement.

The purpose of this study was to document the epidemiology, symptoms and treatment of snake envenomation in Mali between 2005 and 2006. Data was collected using two methods, i.e., household surveys and retrospective surveys. Household surveys carried out in a village of 597 people showed that the annual average incidence was 164 snakebites per 100,000 inhabitants. Retrospective surveys were conducted in 35 healthcare facilities (5 regional hospitals and 30 district health centers) located in 5 parts of the country. Study periods ranged from 2 to 11 years depending on the location. The mean annual incidence of snakebite including dry-bites without envenomation was 27 per 100,000 inhabitants (range, 15-59). Hospital mortality was 4.7% (67/1433) (range, 2.2-6.7%). The population at risk consisted mainly of working men who accounted for 68.4% (980/1433). Patients between 15 and 30 years accounting for 41.2% (590/1433) of the sample were at highest risk for snakebite (chi2=9.96; p=6.10-3). The frequency of snakebite increased from 9.9% (142/1433) in Mopti in the North to 39.9% (572/1433) in Sikasso in the South (chi2=11.93; p=0,017). Snakebites most frequently occurred during the rainy season (56.6%) but only 0.68% of victims were referred to the health center. Hemorrhagic and inflammatory syndromes were the main complications of envenomation. Treatment was always symptomatic. Antivenom serum requirements ranged from 63 to 200 ampoules per year. Our results show that the frequency of snakebites remains grossly underestimated based on hospital data.