Write a note on the causative agent and symptoms of typhoid fever.

(N/A) Typhoid fever in humans is caused by the pathogenic bacterium $Salmonella$ $typhi$.
$Salmonella$ $typhi$ generally enters the small intestine of the human body through contaminated food and water.
They migrate through the blood to reach different organs. Lysed bacteria release toxins that have severe effects on the human body.
Sustained high fever ($39$-$40$ $^{\circ}C$),weakness,stomach pain,constipation,headache,and loss of appetite are common symptoms of this disease.
In severe cases,it may lead to intestinal perforation and death.
Typhoid vaccines are available,and the $Widal$ test is used for the diagnosis of typhoid fever.