I didn't had much time for this discussion today, but  Kiddo asked some clarification, here you go...

Here is a little history of infectious virus origination. Unlike other disease like malaria, cholera, measles these are not necessarily  transmitted through unhygienic conditions of Africa. And most of the modern epidemic started after the vaccination revolution and new drugs testing. 

Marburg virus:

In 1967, 31 workers at a laboratory in Marburg, Germany began suffering from an array of horrifying symptoms: fever, diarrhea, vomiting, and massive bleeding from a variety of internal organs. Seven of the workers would eventually succumb to their illnesses.

After an extensive investigation, scientists identified the source of the outbreak, a pair of grivet monkeys imported from Uganda for polio research. The primates were carrying a shocking, never-before-seen virus, which later was named Marburg for the city in which it was discovered

Ebola:

The first reported case of the deadly virus came in 1976 and it is named after the Ebola River in the Democratic Republic of Congo which was where it was discovered. At the time, the area where the disease was spotted was officially recognized as Zaire. The virus has since spread throughout the region.

Non-human primates, like gorillas and chimpanzees, have been cited by the World Health Organization as possible infection sources for humans, but experts have realized that they are not the source of the problem. The apes have been deemed “accidental hosts,” meaning that they catch the disease and then pass it along but are not the initial “reservoir” source that produces the virus.

HIV Virus:

• In the late 1950s, several different groups of researchers were developing vaccines against polio, which at the time was still epidemic worldwide. One of these vaccines, developed by Hilary Koprowski, MD (1916-2013), was used in trials in Africa, after first being tested in the United States. The vaccine virus was grown in tissue cultures taken from macaque monkeys before being administered to about a million people in Burundi, Rwanda, and what is now the Democratic Republic of the Congo. The location coincides dramatically. The earliest known cases of AIDS occurred in central Africa, in the same regions where Koprowski's polio vaccine was given to over a million people in 1957-1960. Polio vaccines are grown (cultured) on monkey kidneys which could have been contaminated by SIVs. Polio vaccines could not be screened for SIV contamination before 1985.