What defines a spillover event in the context of Ebola virus?

What defines a spillover event in the context of Ebola virus?

• A. Occurs when an animal or human becomes infected with Ebola virus through contact with the reservoir host.
• B. It occurs when a recovered patient transmits the virus via semen to a partner.
• C. It is caused by mosquitoes transmitting the virus from animals to humans.
• D. It occurs only when a person contracts the virus from another infected person.

Answer: (A)

Spillover is the initial cross-species transmission of Ebola from its natural reservoir into a new host, starting an outbreak. For Ebola, the reservoir is thought to be fruit bats, and spillover occurs when a person or an animal comes into contact with infected bat tissues, fluids, or contaminated materials (such as bushmeat). Once this cross-species jump happens, human-to-human transmission can occur through direct contact with bodily fluids, driving the spread in the population. The other scenarios describe downstream transmission after spillover: sexual transmission from a recovered person via semen, vector-like transmission by mosquitoes (not a known route for Ebola), and transmission only between infected people without involving a contact with the reservoir. These do not define spillover, which is specifically the cross-species introduction from reservoir to a new host.

Spillover is the initial cross-species transmission of Ebola from its natural reservoir into a new host, starting an outbreak. For Ebola, the reservoir is thought to be fruit bats, and spillover occurs when a person or an animal comes into contact with infected bat tissues, fluids, or contaminated materials (such as bushmeat). Once this cross-species jump happens, human-to-human transmission can occur through direct contact with bodily fluids, driving the spread in the population.

The other scenarios describe downstream transmission after spillover: sexual transmission from a recovered person via semen, vector-like transmission by mosquitoes (not a known route for Ebola), and transmission only between infected people without involving a contact with the reservoir. These do not define spillover, which is specifically the cross-species introduction from reservoir to a new host.