A person complaining of stomach ache, weakness, and sustained high fever was recommended a "Widal test" by the doctor.

Identify the pathogen responsible for the disease the person is suffering from: 

Salmonella typhi.

The correct answer is Option (3) –Salmonella typhi.

Salmonella typhi is a pathogenic bacterium which causes typhoid fever in human beings. These pathogens generally enter the small intestine through food and water contaminated with them and migrate to other organs through blood. Sustained high fever (39° to 40°C), weakness, stomach pain, constipation, headache and loss of appetite are some of the common symptoms of this disease. Intestinal perforation and death may occur in severe cases. Typhoid fever could be confirmed by Widal test .