Write the names of three diseases caused by viruses. Give a full account of any one of them.

(N/A) Three diseases caused by viruses are:
$(a)$ Influenza
$(b)$ Hepatitis
$(c)$ $AIDS$
Detailed account of $AIDS$ (Acquired Immuno Deficiency Syndrome):
Cause: It is caused by the retrovirus $HIV$ (Human Immuno Deficiency Virus).
Mode of Transmission:
$(i)$ Blood transfusion.
$(ii)$ Unprotected sexual contact.
$(iii)$ Use of contaminated needles and syringes,sharing razors,or piercing instruments.
$(iv)$ From an infected mother to the developing foetus through the placenta.
Symptoms:
$(i)$ Prolonged fever.
$(ii)$ Swollen lymph glands.
$(iii)$ Significant weight loss and loss of appetite.
$(iv)$ Unexplained bleeding.
$(v)$ Decreased count of blood platelets causing haemorrhage.
$(vi)$ Loss of memory and mental ability.
$(vii)$ The patient becomes highly susceptible to opportunistic infections.
Detection:
It is detected using the $ELISA$ test and the Western Blot test.
Prevention:
$(i)$ Practicing safe sex.
$(ii)$ Use of disposable syringes,needles,and fresh razors.
$(iii)$ Mandatory testing of blood before transfusion.
$(iv)$ Public education through $AIDS$ awareness programmes.
$(v)$ Avoiding pregnancy in $HIV$-infected mothers.
Treatment: There is no permanent cure for $AIDS$ so far; only antiretroviral therapy is used to manage the viral load.