Virus infections (viral infections)

There are approximately 200 pathogenic (= pathogenic) viruses known to cause very different diseases (including colds, flu, meningitis, inflammation, measles, smallpox, cold sores, shingles, yellow fever, hepatitis, AIDS, etc.).
Viruses are very small, not with the naked eye micro-organisms, DNA (including herpes and smallpox) or RNA (eg flu, colds, measles, hepatitis, warts, HIV and cancer or