They also cause severe illnesses such as HIV/AIDS, smallpox and hemorrhagic fevers. Viruses are like hijackers. They invade living, normal cells and use those cells to multiply and produce other viruses like themselves. [fpnotebook.com]

Viruses cause familiar infectious diseases such as the common cold, flu and warts. They also cause severe illnesses such as HIV/AIDS, smallpox and hemorrhagic fevers. Viruses are like hijackers. [fpnotebook.com]