Question

If someone is suffering from cold and cough in the class, it is likely that the children sitting around will be exposed to the infection. But all of them do not suffer from the disease. Why?

Answer 1

Although many catch cold or cough easily, some don't fall sick easily!
It's because their body possess immunity power!
Their body has induced antibodies to fight against the infectious microbes if they enter their body. Thus, we need to improve our immunity strength.
For that, we should include fresh fruits and vegetables in our regular diet. And exercise regularly and maintain our physical fitness.
Thanks

Answer 2

Cold is mainly due to the rhino virus.

it is spread by using the pen, pencil of the infected student.

and if the infected student do not take care while coughing and sneezing it is spread to the others. But not all the students because it depends of the immunity of the students.

Someone having good immunity to fight against the infection while some of them are failed to fight back because of the weak immunity.

Those who fails to fight back may suffer from cold.

Hope it's useful.

All the best