health

Symptoms Symptoms vary widely, depending on the virus and the
organs involved. Many viruses, like many bacteria, cause fever, and either
respiratory symptoms (coughing and sneezing) or intestinal symptoms
(nausea, vomiting, diarrhea). Viral illnesses often cause high fevers in
young children, even when the illnesses are not dangerous.


Diagnosis Some viral infections, such as influenza, the common
cold, and chickenpox, are easily recognized by their symptoms and no
lab tests are needed. For many others, such as viral hepatitis, AIDS,
and mononucleosis, a blood sample is analyzed for the presence of specific
antibodies to the virus. If present, these antibodies help confirm
the diagnosis. In some cases, a virus may be grown in the laboratory,
using a technique called tissue culture*, or identified by its nucleic
acid, using a technique called polymerase chain reaction (PCR). Tests
such as tissue culture or PCR are used when antibody tests are not
precise enough or when the actual amount of a virus in the body must
be determined.


Treatment Viruses cannot be treated with the antibiotics that kill bacteria.
Fortunately, a few drugs, such as ribavirin and acyclovir, can control
the spread of viral invaders without destroying host cells. Intense research
to find better treatments for AIDS led to development of many drugs
that help fight the virus. Unfortunately, as of 2009, none of these drugs
was able to treat viral infections as effectively as antibiotics treat bacterial
infections.