To make closed object questions, we often put the verb before the subject. This is called inversion.
Question
Is Malaria prevalent?
Are diseases deadly?
Can Malaria kill?
Affirmative
Malaria is prevalent.
Diseases are deadly.
Malaria can kill.
If we are using an auxiliary verb (do, did, does) with the main verb there is no need to use it in the affirmative.
Question
Does Malaria kill?
Do diseases spread?
Affirmative
Malaria kills.
Diseases spread.
To make an open object question we put a Wh- question word before the verb.
Question
Where is malaria prevalent?
How can malaria kill people?
Affirmative
Malaria is prevalent in tropical areas.
It can kill people by infecting the blood.
Subject questions (always open)
In some questions, who or what is the subject of the verb. There is NO inversion of subject and verb in these questions
Question
What is causing these deaths?
How many people died from malaria?
Affirmative
Blood poisoning is the main cause of death. (what is the subject. Blood poisoning is what)
1.3 million people died.
(how many is the subject. 1.3 million is how many.)
Here is an example interview showing how to use follow up questions to get your subject to give additional information: