Human Diseases — Which Pathogen, Which Vector, Which Vaccine

General Science papers ask about disease constantly, and almost every question is one of three shapes: what organism causes it, what creature carries it, and what vaccine prevents it. Students lose these marks not because the facts are hard but because they are stored as a loose pile instead of a table.

So build the table. Every communicable disease belongs to one of four causal groups — bacteria, virus, protozoan, or worm — and the group is what most questions actually test. Malaria is the classic trap: the mosquito is only the vector, the cause is a protozoan called Plasmodium. Confuse carrier with cause and you lose the mark even though you knew everything about the disease.

A second axis matters just as much: how it spreads. Air, water, contact, or a living vector. Cholera and typhoid travel by water, so their control is sanitation. Dengue and malaria travel by mosquitoes, so their control is stagnant water. Knowing the route often gives you the answer even when the pathogen's name has slipped.

1. Malaria in humans is caused by which kind of organism?

2. Dengue fever is transmitted to humans by which mosquito?

3. The BCG vaccine given in early childhood protects mainly against which disease?

4. Kala-azar (visceral leishmaniasis) is transmitted by the bite of which insect?

5. Which one of the following diseases is caused by a virus?

6. Filariasis, or elephantiasis, is caused by the worm Wuchereria bancrofti and is spread by which mosquito?

7. In which year did the World Health Organization declare smallpox eradicated from the world?

8. The DPT vaccine protects a child against which three diseases?