Echo virus, an enterovirus, is spread via the fecal-oral route and causes aseptic meningitis (b). Coronaviruses (a) are more commonly spread via respiratory droplets and cause the common cold. HIV (c), the causative agent of AIDS, is spread via blood and sexual contact. Influenza virus (d) is spread by respiratory droplets and causes influenza and sometimes primary viral pneumonia. Rabies virus (e) is spread by bites of mammals and causes the CNS disease rabies.