Ebola virus disease (EVD) is a severe, often fatal illness in humans. It is a zoonosis affecting both humans and nonhuman primates (NHPs), namely monkeys, gorillas and chimpanzees. The virus is transmitted to humans from wild animals, with the natural reservoir now thought to be African fruit bats. Transmission is believed to occur from handling and eating raw or under cooked meat from infected bats or NHPs. It is also possible for transmission to occur from eating fruit contaminated with bat saliva or feces, or from hands coming into contact with surfaces with infected bat droppings and then touching one’s eyes, nose or mouth.
The current EVD case fatality rate is around 40%, but case fatality rates have varied from 25% to 90% in past outbreaks. The first EVD outbreaks occurred practically simultaneously in 1976 in remote villages of the Democratic Republic of Congo (DRC) and in Sudan. The sources of transmission of the two species of Ebola virus involved, that is, the Zaire ebolavirus in the DRC outbreak and the Sudan ebolavirus in the Sudan outbreak, remain unknown. The next outbreak occurred in 1994 in the Ivory Coast. Subsequent localized outbreaks have occurred in other countries, but the most recent outbreak in West Africa (mainly Liberia, Sierra Leone and Guinea) has affected major urban areas. Imported cases in Nigeria, Mali and Senegal were contained, demonstrating the effectiveness of rapid response and traditional quarantine measures. Ebola virus has also been imported into a number of countries in the developed world. This is the most serious Ebola outbreak so far and as of 29 January 2015, 22,000 people have been infected with around 8,800 deaths reported in Guinea, Sierra Leone and Liberia.
Ebola viruses consist of five genetically distinct members of the Filoviridae family with the Zaire ebolavirus constituting the most serious threat to both humans and NHPs in Sub-Saharan Africa because of its high case fatality. It has also caused the largest number of outbreaks, including the present one, where the average risk of death among those infected is currently 40%.
The incubation period is 2 to 21 days, with an average of 8–10 days. Humans are not infectious until they develop symptoms. Initial symptoms are the sudden onset of fever, fatigue, muscle pain, headache and sore throat, followed by vomiting, diarrhea, abdominal (stomach) pain, rash, symptoms of impaired kidney and liver function, and in some cases, both internal and external bleeding. In cases that become fatal, death usually occurs 9–10 days after the onset of symptoms. If the patient survives past the second week of infection, there is a significantly increased likelihood of survival.
Ebola virus spreads from person-to-person through direct contact with tissue, organs, blood or bodily fluids from an infected person and especially a deceased patient, and through surfaces and materials contaminated with these fluids. The virus enters the body through broken skin or mucous membranes and is not airborne; however, a cough from a sick person could infect someone who has been sprayed with infected saliva. The virus is also present on a patient’s skin after symptoms develop.
The World Health Organization (WHO) has stated that community engagement is key to successfully controlling outbreaks and relies on applying a suite of interventions, namely case management, surveillance and contact tracing, good laboratory services, safe burials and social mobilization. Early supportive care with rehydration and treatment of symptoms improves rates of survival. There is as yet no licensed treatment proven to neutralize the virus but a range of blood, immunological and drug therapies are under development. There are currently no licensed Ebola vaccines but potential candidates are undergoing evaluation.
The Ebola outbreak has had a severe humanitarian impact in that economic activity, including farming, food processing and food distribution, has been disrupted and is a potential threat to the entire food supply, especially for urban consumers. Individuals, families and communities that were exposed to a symptomatic EVD patient may be subject to a 21-day quarantine. Inadequate provision of food and other support to those quarantined has resulted in individuals violating the cordon sanitaire.
As part of the unified response under the UN Mission for Ebola Emergency Response, the World Food Programme (WFP) has made food assistance available to over 1.3 million people and is involved in various humanitarian efforts in the affected countries. WFP has provided food assistance to patients in Ebola treatment centers, survivors of Ebola who are discharged from treatment centers and communities with widespread and intense transmission—including the families of people infected with Ebola who are in treatment, deceased or recovering. This assistance helps to stabilize affected communities by enabling them to limit unnecessary movement.
Ebola is regarded as a foodborne disease in those countries with bush meat traditions. Bush meat is an important source of protein where other sources of animal protein are scarce or too expensive. It is important that the risk of wildlife-to-human transmission from contact with infected fruit bats or NHPs and/or consumption of their raw or under cooked meat is reduced. The Ebola virus is inactivated by thorough heating of animal products (meat and blood) for 60 minutes at 60 °C or boiling for 5 minutes. Basic hygiene measures such as regular handwashing, handling potentially infected meat with gloves and changing of clothes, boots and other protective clothing before and after touching these animals and their products are important to reduce potential transmission and, of course, sick, diseased or dead animals should never be consumed. The virus can survive in liquid or dried material for days, but is vulnerable to attack by chemical disinfectants, such as soap, household bleach, chlorine dioxide, hydrogen peroxide and most other disinfectants. It is not inactivated by freezing or refrigeration.
In affected countries, persons working in the food industry who have early symptoms of EVD should be sent immediately to the nearest clinic for evaluation. Those who have been exposed to Ebola virus should be restricted from going to work for the 21-day maximum incubation period to prevent possible transmission of EVD to other coworkers.
Fortunately, the number of new cases of EVD has dropped significantly with WHO reporting fewer than 100 cases during the week of January 18–24, 2015. However, scientists have warned that the virus is mutating and that the number of asymptomatic cases is unknown.
Lucia Anelich, Ph.D., and Gerald G. Moy, Ph.D., are both independent food safety consultants who prepared a scientific information bulletin (SIB) for the International Union of Food Science and Technology (IUFoST) on this topic. This article reflects a summary of that SIB.