The outbreak was traced to infected vervet monkeys cut up in the labs for polio research; they came from close to the present outbreak in Uganda.

• 其病毒的蔓延可追溯到在实验室因脊髓灰质炎的研究而致死的受感染的黑长尾猴，这些猴子来自最近爆发疾病的乌干达。