Which infection is likely present in a person who has developed interferons in their body?

Measles

The presence of interferons in the body indicates that the person is likely carrying an infection of measles.

Interferons are proteins that are produced by cells in response to viral infections. They play a crucial role in the body's antiviral defense mechanisms by inhibiting viral replication and spreading to other cells. Measles is a highly contagious viral infection caused by the measles virus. When the body detects the presence of the measles virus, it triggers the production of interferons to help combat the infection.

On the other hand, typhoid is caused by the bacteria Salmonella typhi, filariasis is caused by parasitic worms of the genus Wuchereria, and malaria is caused by the Plasmodium parasite. While these infections may elicit immune responses, interferons are specifically associated with viral infections rather than bacterial or parasitic infections.

Therefore, the correct answer is (d) measles, as the presence of interferons suggests a viral infection.