UPSC Civil Services Model Paper 8

A wide range of organisms belonging to bacteria, viruses, fungi, protozoans, helminths, etc. could cause diseases in man. Such disease-causing organisms are called pathogens Salmonella typhi is a pathogenic bacterium that causes typhoid fever in human beings.
Hence, Statement 1 is correct.
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 the Widal test Bacteria like Streptococcus pneumonia and Haemophilus influenza are responsible for the disease pneumonia in humans which infects the alveoli (air-filled sacs) of the lungs. Hence, Statement 2 is correct.
As a result of the infection , the alveoli get filled with fluid leading to severe problems in respiration.
The symptoms of pneumonia include fever, chills, cough, and headache.
In severe cases, the lips and fingernails may turn grey to bluish in colour.
A healthy person acquires the infection by inhaling the droplets/aerosols released by an infected person or even by sharing glasses and utensils with an infected person.
Dysentery, plague, diphtheria, etc. are some of the other bacterial diseases in man.
Some of the human diseases are caused by protozoans too.
Plasmodium , a tiny protozoan is responsible for this disease .
Different species of Plasmodium ( P. vivax, P. malaria, and P. falciparum ) are responsible for different types of malaria . Hence, Statement 3 is correct.
Of these, malignant malaria caused by Plasmodium falciparum is the most serious one and can even be fatal.