And so in the 1940s, a group of people led by Collier started to develop a large scale production method for making a reliable source of vaccinia virus.
While the source of the virus remains unknown, further surveillance will help in understanding its transmission, said Liang Wannian, director general of the health emergency division of China's National Health and Family Planning Commission.
Diosdado Nsue-Micawg, the WHO representative in the Angolan capital of Luanda, said the health agency does not know the source of the virus, but fears that hunters and women who visit the forest might have been in contact with infected monkeys.
