Science of spread
TO UNDER STAND Ebola's potential to spread, the US government agency Centers for Disease Control and Prevention constructed a modelling tool called Ebola-Response. Its projections say that the spread of Ebola will begin to decrease and eventually end if approximately 70 per cent of patients are in medical care facilities. Every 30-day delay in increasing the percentage of patients in treatment units to 70 per cent will cause an approximate tripling of the number of daily cases that occur at the peak of the epidemic. Another study based on a mathematical transmission model shows that if the epidemic continues in its present course in Montserrado, Liberia's most populous county, there could be 170,996 cases and 90,122 deaths in the county by December 15. Some 97,940 cases of the disease can be averted if control measures are started by October 31. The study, published in The Lancet Infectious Diseases on October 23, says if the interventions are delayed till November 15, just over half of these cases would be averted.