The Ebola curve

EVD Outbreak Week 40 (PDF):

The total number of confirmed, probable, and suspected cases (see Annex 1) in the West African epidemic of Ebola virus disease (EVD) reported up to the end of 5 October 2014 (epidemiological week 40) is 8033 with 3865 deaths. Countries affected are Guinea, Liberia, Nigeria, Senegal, Sierra Leone, and the United States of America. A confirmed case of EVD has been reported in Spain, but because the case was confirmed during the week ending 12 October (epidemiological week 41), information on this case will be included in the next Ebola Response Roadmap update.

The past week has seen a continuation of recent trends: the situation in Guinea, Liberia, and Sierra Leone continues to deteriorate, with widespread and persistent transmission of EVD. Problems with data gathering in Liberia continue. It should be emphasized that the reported fall in the number of new cases in Liberia over the past three weeks is unlikely to be genuine. Rather, it reflects a deterioration in the ability of overwhelmed responders to record accurate epidemiological data. It is clear from field reports and first responders that EVD cases are being under-reported from several key locations, and laboratory data that have not yet been integrated into official estimates indicate an increase in the number of new cases in Liberia. There is no evidence that the EVD epidemic in West Africa is being brought under control, though there is evidence of a decline in incidence in the districts of Lofa in Liberia, and Kailahun and Kenema in Sierra Leone.

Recall that back in July, it was reported: “The current outbreak is the worst ever. So far 467 people have died and
health staff have identified at least 292 other suspected or confirmed
That was back in Week 25, so in the subsequent three months, we’ve seen the officially confirmed number of cases increase by 10.6, or if you prefer to put it in scary percentage terms, 958 PERCENT! According to this doubling calculator, the time in which it takes the outbreak to double is 4.39 weeks, so we’ll know that if the Week 41 report contains more than 9,862 confirmed cases, the outbreak is picking up its pace. Either way, the slope of that curve in confirmed cases from Week 25 to Week 40 looks rather problematic.

As for the likelihood that anything but a complete travel ban will stop the continued spread of the virus, consider this report from the CDC entitled “Epidemiology of Travel-associated Pandemic (H1N1) 2009 Infection in 116 Patients, Singapore”:

The fact that one fourth of the case-patients in our study boarded a plane after becoming ill and traveled despite having symptoms illustrates the role of travelers in disseminating infection in a highly interconnected world. It raises the question of whether exit screening should be considered. However, the effectiveness of exit screening will depend on the role of asymptomatic persons in transmission, and such screening will still miss persons who are incubating the infection. Exit screening would severely hinder international travel, and because of its questionable efficacy, it may not be justified and may be contrary to the intent of the International Health Regulations 2005.

So, wash your hands, stock up a bit, and avoid any unnecessary travel, that would be my advice. School vacation time is coming up in many countries in Europe in the next two weeks, so a lot of people have travel plans as a result. If things are going to go seriously south, we should know it in the next 4-6 weeks. To the right is a zoomed-in curve based on the actual confirmed cases reported by WHO from Weeks 34 to 40, added onto an averaged curve from the reported cases in Week 25. WHO only began releasing the reports in Week 34, but during those six weeks, the outbreak has gone from 3,000 to 8,000 officially confirmed cases.