Following the non-detection of new Ebola cases in Senegal and Nigeria after the requisite 42 days of active surveillance that is currently in place, the World Health Organisation is set to declare the end of the outbreak of Ebola Virus Disease, EVD, in the two countries. The anticipated declaration that the Ebola outbreaks in the two countries are over, is expected to give the world some welcome news, even as the EVD epidemic remains out of control in Liberia, Sierra Leone and Guinea.
The death toll so far in the outbreak, first reported in Guinea in March 2014, has reached 4,447 from a total of 8,914 cases. Total number of cases in West Africa, are expected to top 9,000 this week. In a “Ebola situation assessment Report” released yesterday, the global health body said the end of the outbreak of EVD will be declared in Senegal on Friday October 17, 2014, while the declaration for Nigeria will be made on Monday, October 20, 2014. In the statement, WHO confirmed that tracing of people known to have contact with an Ebola patient reached 100 percent in Lagos and 98 percent in Port Harcourt.
“In a piece of world-class epidemiological detective work, all confirmed cases in Nigeria were eventually linked back to the Liberian air traveller who introduced the virus into the country on 20 July,” the WHO noted, explaining that 95 percent of confirmed Ebola cases have an incubation period in the range of 1 to 21 days while 98 percent have an incubation period that falls within the 1 to 42 day interval. Further, the WHO explained that the outbreak in the two countries have been far smaller than in other West African countries, with 19 confirmed cases and eight deaths in Nigeria, where the last reported case was on September 5, 2014, according to the Centres for Diseases Control, CDC, while the single confirmed case in Senegal was in late August, where the infected person survived.
The WHO, it was gathered, is therefore confident that detection of no new cases, with active surveillance in place, throughout this 42-day period means that an Ebola outbreak is indeed over. To declare the end of an Ebola outbreak, a WHO sub-committee on surveillance, epidemiology, and laboratory testing establishes the date of the end of an Ebola outbreak, according to rigorous epidemiological criteria that include the date when the last case with a high-risk exposure completes 21 days of close medical monitoring and tests negative for the virus.
According to WHO recommendations, health care workers who have attended patients or cleaned their rooms should be considered as “close contacts” and monitored for 21 days after the last exposure, even if their contact with a patient occurred when they were fully protected by wearing personal protective equipment. For health care workers, the date of the “last infectious contact” is the day when the last patient in a health facility tests negative using a real-time reverse-transcriptase polymerase chain reaction (RT-PCR) test.
For WHO to declare an Ebola outbreak over, a country must pass through 42 days, with active surveillance demonstrably in place, supported by good diagnostic capacity, and with no new cases detected. Active surveillance is essential to detect chains of transmission that might otherwise remain hidden.