I don't think there are any liars, it is complicated. See [Bausch, et. al., Assessment of the Risk of Ebola Virus Transmission from Bodily Fluids and Fomites, Journal of Infectious Diseases, Volume 196, Issue Supplement 2, Pp. S142-S147] for a detailed discussion.
When a viurs replicates, it eventually leaves the infected cell/tissue; this is called shedding. How concentrated it is in any particular cell/tissue is highly variable, and how this correlates with symptom severity is variable as well. So, you could have in one case someone who is infected by briefly brushing up against someone's exposed skin who beats the odds and gets infected, because the diseased person was shedding at the just the right time, and because the person who brushed against them was susceptible (broken skin).
On the other hand, you could have someone working with infected persons closely, who never gets infected. I've worked with dangerous pathogens, and chemical agents, and it only takes one little mistake to get exposed. I once got several million toxic doses of tetrodotoxin dumped on me (beaker got bumped and spilled in my lap), but no broken skin, so no symptoms. Could just as easily have been dead in seconds. It is the nature of the beast, and it is not a simple black and white always this or always that. Best to err on the side of caution.
H'mmm, tetrodotoxin. If my hazy memory serves me correctly, cone shells, the blue-ringed octopus (via bacteria in its mouthparts) and the puffer fish (the delicacy fugu in Japan; concentrated in the ovaries and liver). Blocks up calcium channels in nerve cells, or similar, right? What on earth were you researching tetrodotoxin for? Given the topic, NO cheers.