Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Viral Infections ?
    ### Response:
    Viruses are capsules with genetic material inside. They are very tiny, much smaller than bacteria. 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.
    