The last MS-DOS viruses were seen in the wild in Cuba not very long ago. Researchers believe the last virus lived the last chapter of its life in Cuba. Victor Manuel Alvarez, the creator of the malware research tool YARA, is a Cuba native. When Alvarez was a teenager, it was common to see PCs that were 10, 15 or even 20 years old, he says. The country has some of the oldest computers still in use, and it was likely the place where the last viruses were found.”]
Source: https://www.csoonline.com/article/3409790/hunting-vintage-ms-dos-viruses-from-cuba-to-pakistan.html