TRANSMISSION
It is thought that fruit bats of the Pteropodid family are natural Ebola virus hosts. Ebola is introduced into the human population through close contact with the blood, secretions, organs or other bodily fluids of infected animals such as fruit bats, chimpanzees, gorillas, monkeys, forest antelope or porcupines found ill or dead or in the rainforest. Ebola then spreads through human-to-human transmission via direct contact (through broken skin or mucous membranes) with
• Blood or body fluids of a person who is sick with or has died from Ebola
• Objects that have been contaminated with body fluids (like blood, faeces, vomit) from a person sick with Ebola or the body of a person who died from Ebola
Health-care workers have frequently been infected while treating patients with suspected or confirmed EVD. This occurs through close contact with patients when infection control precautions are not strictly practiced.
Burial ceremonies that involve direct contact with the body of the deceased can also contribute in the transmission of Ebola.
People remain infectious as long as their blood contains the virus.
Ebola is a disease transmitted from wild animals to humans most likely through hunting and collection of sick or dead wild animals and handling or consumption of uncooked bush meat. Although the source of infection for non-human primates often remains unclear, most evidence indicates direct infection from one or more natural hosts. In rural areas fruit bats are a popular source of forest meat for humans and are prepared by hand to be dried, smoked and/or cooked. Infection could also be transmitted to humans by consumption of forest fruits contaminated with bat saliva or faeces
It is recommended that in affected countries contact with wild animals, including bats, rodents or monkeys should be avoided and that communities in contact with these animals practice basic hygiene measures such as regular hand washing at all times. The hunting of susceptible wild animal species listed above for food in affected countries should be avoided.
Human to human transmission occurs through contact with body fluids of an infected person. It is thought that the current epidemics throughout West Africa originated from a single animal-human transmission event that occurred in the forest at the border between Guinea, Sierra Leone and Liberia.
NATURAL HOSTS
Field studies and epidemiological surveys in Africa have demonstrated widespread antibody prevalence to Ebolaviruses in fruit bats suggesting that fruit bats may be natural hosts for EBOV. A recent survey also mentioned the hypothesis of insectivorous bats role (this need to be confirmed). However, when bats and other vertebrate species were experimentally inoculated, only fruit bats became infected and shed virus in faeces without showing any clinical signs.
Monkeys are not considered as natural hosts because of their high sensitivity to the virus and their high mortality rate when infected.
The related Marburg virus has been isolated from fruit bats (Roussettus aegyptiacus) in Uganda.
The role of pigs in EVD epidemiology is unclear. There is no evidence that domestic animals play an active epidemiological role in the transmission of the disease to humans.
Transmission to humans
Ebola is a disease transmitted from wild animals to humans most likely through hunting and collection of sick or dead wild animals and handling or consumption of uncooked bush meat. Although the source of infection for non-human primates often remains unclear, most evidence indicates direct infection from one or more natural hosts. In rural areas fruit bats are a popular source of forest meat for humans and are prepared by hand to be dried, smoked and/or cooked. Infection could also be transmitted to humans by consumption of forest fruits contaminated with bat saliva or faeces.
It is recommended that in affected countries contact with wild animals, including bats, rodents or monkeys should be avoided and that communities in contact with these animals practice basic hygiene measures such as regular hand washing at all times. The hunting of susceptible wild animal species listed above for food in affected countries should be avoided.
Human to human transmission occurs through contact with body fluids of an infected person. It is thought that the current epidemics throughout West Africa originated from a single animal-human transmission event that occurred in the forest at the border between Guinea, Sierra Leone and Liberia.
Ebola disease in humans
The incubation period of EVD in humans is usually 2-21 days.
EVD is transmitted between humans by body fluids such as blood, vomit, urine, saliva, stool (faeces) or semen. An important source of infection for local communities in the affected countries occurs when relatives perform the ritual washing Ebola victims at funerals, bringing them into direct close contact with body fluids and secretions and indirect contact with environment contaminated with such fluids. In some cases, the dead are buried in a shallow grave which is easily discovered by stray dogs which expose the corpse leading to further spread of the disease. Hospital acquired infections are also common in the absence of adequate personal protective equipment and medical supplies.
In August 2014, EVD was detected in the North-western region of the Democratic Republic of Congo (DRC). Epidemiological investigation has linked the index case to the preparation of bush meat for consumption. The causative virus was identified to be ZEBOV but most closely related to ZEBOV from the 1995 DRC outbreak and with no epidemiological link to the outbreak in West Africa.
