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The ratio plays a key role in understanding epidemic dynamics during the 2014\u20132016 Ebola outbreak in Sierra Leone and Guinea. The maximum value of the ratio occurs immediately before or after the time-dependent reproduction number (R<jats:sub><jats:italic>t<\/jats:italic><\/jats:sub>) equals 1, depending on the initial susceptible population (<jats:italic>S<\/jats:italic>(0)). It is demonstrated that transmission rate curves corresponding to various incubation periods intersect at a single point referred to as the Cross Point (CP). At this point, the <jats:italic>E\/S<\/jats:italic> ratio reaches an extremum, signifying a critical shift in transmission dynamics and aligning with the time when R<jats:sub><jats:italic>t<\/jats:italic><\/jats:sub> approaches 1. By plotting transmission rate curves, <jats:italic>\u03b2<\/jats:italic>(<jats:italic>t<\/jats:italic>), for any two arbitrary incubation periods and tracking their intersections, we can trace CP over time. CP serves as an indicator of epidemic status, especially when R<jats:sub><jats:italic>t<\/jats:italic><\/jats:sub> is close to 1. It provides a practical means of monitoring epidemics without prior knowledge of the incubation period. Through a case study, we estimate the transmission rate and reproduction number, identifying CP and R<jats:sub><jats:italic>t<\/jats:italic><\/jats:sub>\u2009=\u20091 while examining the <jats:italic>E\/S<\/jats:italic> ratio across various values of <jats:italic>S<\/jats:italic>(0).<\/jats:p>","DOI":"10.1038\/s41598-024-62719-3","type":"journal-article","created":{"date-parts":[[2024,5,27]],"date-time":"2024-05-27T19:01:43Z","timestamp":1716836503000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["A novel indicator in epidemic monitoring through a case study of Ebola in West Africa (2014\u20132016)"],"prefix":"10.1038","volume":"14","author":[{"given":"Minkyu","family":"Kwak","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xiuxiu","family":"Sun","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yunju","family":"Wi","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kyeongah","family":"Nah","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yongkuk","family":"Kim","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hongsung","family":"Jin","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2024,5,27]]},"reference":[{"key":"62719_CR1","doi-asserted-by":"publisher","first-page":"110","DOI":"10.3201\/eid1201.050593","volume":"12","author":"S Cauchemez","year":"2006","unstructured":"Cauchemez, S. et al. 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