The number of deaths traced to the current Ebola outbreak now exceeds 5000. The rate of transmission has not increased in Guinea and has slowed in Liberia. But the situation in Sierra Leone is continuing to worsen. A new network of Ebola cases has emerged in Mali among health workers who were exposed while caring for a man with kidney failure. The patient was also suffering from a non-diagnosed Ebola infection.
The fatality rate among those exposed to the Ebola virus is falling. In June the fatality rate for this West African outbreak was estimated at 90 percent. In September the fatality rate was still at least seventy percent. In prior Ebola outbreaks — much smaller in scope — the fatality rate has averaged 50 percent of those infected. There are some studies that suggest with early intervention the fatality rate is now as low as 25 percent.
These are small and still unconfirmed studies. But on a preliminary basis it is reasonable to observe:
- The amount of circulating viral load was higher in those who died than in survivors; those patients with the highest levels of virus were most likely to die.
- One of the strongest determinants of survival appears to be patient age. Patients older than 40 years were nearly 3.5 times more likely to die than those aged less than 40. The association between an older age and a higher risk of death was found regardless of whether the patient had co-morbidities or not.
- Evidence of substantial fluid loss and profound electrolyte derangement associated with severe diarrhoea appears to increase the risk of a fatal outcome. More aggressive supportive care, especially intravenous rehydration, is thought to improve the prospects of survival.
Seriously compromising the ability to provide early diagnosis and care is a public health infrastructure insufficient to conduct the necessary contact-tracing. According to the November 12 WHO update:
Between 3 and 8 November, 5301 new contacts were identified in Guinea, Liberia and Sierra Leone, compared with 4067 new contacts traced in the previouwoulds week. A total of 95% (124,214 of 130,140) of required daily contact visits were conducted. However, the proportion of contacts reached was lower in many districts. Each district is reported to have at least one contact-tracing team in place. On average, only 10 contacts were listed per case in the three countries in the past week. The low average number of contacts listed per case suggests that the estimate of 95% gives an unduly favourable view of the success of contact tracing. Active case finding teams are being mobilized as a complementary case detection strategy.
The situation in West Africa remains very bad, but it is not — yet? — as bad as some projected in September or even early October. The predictions have, in part, been disrupted by increased public health interventions, improved clinical care, and — especially — altered population behavior. While the threat of the virus was too long underplayed, since August a creative and committed response has paid-off.
In recognition of the continuing high risks, Médecins Sans Frontières (MSF), an NGO with deep experience in the region, has recommended a new strategic approach, “Agile and well-equipped rapid response teams should be deployed quickly to actively investigate hotspots wherever they occur, and mount a comprehensive response.” This approach would depend much less on the construction and operation of isolation-and-treatment centers.
The rainy season is coming to an end in West Africa. Typically the dry season sees a substantial increase in population movements. This increased mobility will threaten the fragile progress that has been made. The current ten-day forecast for Monrovia predicts almost daily rain and thunderstorms. But early December is predicted to be bright and sunny.
Meeting early today in Brisbane the G20 affirmed and expanded commitments to fight Ebola in West Africa. The world’s leading economies also signaled that more needs to be done to prevent and mitigate infectious threats much worse than Ebola: “This outbreak illustrates the urgency of addressing longer-term systemic issues and gaps in capability, preparedness and response capacity that expose the global economy to the impacts of infectious disease.”