New research from Arizona State University and the University of Tokyo that analyzes transmission rates of Ebola in West African countries shows how rapidly the disease is spreading. Researchers Gerardo Chowell-Puente, PhD, and Hiroshi Nishiura, MD, PhD, have found that each case of Ebola consistently has resulted in the transmission of at least one new case of the disease. Specific analysis of transmission rates in Liberia and Sierra Leone shows on average between one and two new cases for every existing case.
“Our analysis of the reproduction numbers of Ebola cases shows continuous growth from June to August 2014 that signaled a major epidemic,” Nishiura says. “Uncontrolled cross-border transmission could fuel a major epidemic to take off in new geographical areas as was seen in Liberia.”
Rates of transmission increased from June to July in Sierra Leone and Liberia from 1.4 to 1.7 respectively for every existing case. The statistical analysis is detailed in the paper, “Early transmission dynamics of Ebola virus disease, West Africa, March to August 2014,” published in Eurosurveillance.
“Our findings suggest that control of the Ebola epidemic could be attained by preventing more than half of the secondary transmissions for each primary case. This could be attained by isolating those with Ebola and tracing each case to its source,” Chowell says. “Characterizing the distribution of secondary cases from a single case can help healthcare workers and officials understand Ebola transmission dynamics over time in affected countries and gauge the effect of interventions to control spread of the disease,” he adds.
Researchers analyzed case counts by the World Health Organization as of Aug. 26, 2014. Two groups of data were used: confirmed and probable cases; and the total number of reported cases (confirmed, probable, and suspected cases). Read the study.
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