[4] Shortly after graduation, he began to work with smallpox expert Allan Watt Downie in the Department of Bacteriology at the University of Liverpool.

[5] Dumbell's early aptitude for research resulted in the publication of his first paper with Downie in 1947, describing the cultivation of the smallpox virus on the chorioallantoic membrane of hen's eggs.

[6] Dumbell was head of the Virology Department at St Mary's Hospital, London, and on this position one of the key international experts on smallpox.

[7] He used the gene cloning technique to copy fragments of smallpox viral DNA into bacteria, where they could be safely archived and studied later.

[1][9] Following the Declaration, World Health Organization ordered consolidation of virus strain collections worldwide into two high-secure (BSL-4) facilities in the United States and Russia and destruction of the remaining unneeded samples.