Final answer:
Viruses that load from USB drives when a computer starts are known as boot sector viruses or USB viruses. They infect the computer during the boot process and are thus hard to detect and prevent.
Step-by-step explanation:
Viruses that load from USB drives left connected to computers when computers are turned on are known as boot sector viruses or USB viruses. These viruses take advantage of the boot process to execute malicious code before the operating system fully loads, making them particularly dangerous and hard to detect. Unlike latent viruses, which remain dormant, boot sector viruses are active from the start. It's important to note that not all viruses from USB drives are boot sector viruses. Safe computing practices, such as scanning USB drives for viruses and enabling boot protection in your computer's BIOS, can help prevent these types of infections. Viruses, whether dormant or active, play a significant role in various types of infections not only in technology, but in biological systems as well.