Tumor virus

Cancer is not obviously contagious, but one virus, called Rous chicken sarcoma virus (RSV) was discovered that could induce tumors in chickens after being filtered from a mashed tumor. RSV became known as the first oncogenic retrovirus that could be used to study the development of cancer molecularly.
 Francis Peyton Rous United States 1911 Tumor virus

Cancer is not obviously contagious, but one virus, called Rous chicken sarcoma virus (RSV) was discovered that could induce tumors in chickens after being filtered from a mashed tumor. RSV became known as the first oncogenic retrovirus that could be used to study the development of cancer molecularly.