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 oncovirussen, OH-virus, rubella virus, cytomegalo viruses, etc.) contain.
Viruses multiply (= replication) in cells of other organisms (= host), after which they spread on other cells and multiply further.
After infection with a virus develops the body itself is mostly effective resistance (= immunity) to disarm the intruder (eg natural resistance to colds and flu). This is not always the case (eg in HIV / AIDS).

Possible symptoms
The symptoms of viral infections are highly dependent on the nature, location and duration of infection, the condition of the immune system (= immune) and general mental and physical condition.