The correct answer is option 2, Influenza. Influenza is a viral disease caused by the influenza virus. It is a highly contagious respiratory illness that can affect people of all ages. The influenza virus can easily spread from person to person through droplets when an infected person coughs, sneezes, or talks.

Option 1, Diphtheria, is not a viral disease but a bacterial infection caused by the bacterium Corynebacterium diphtheriae. It primarily affects the respiratory system.

Option 3, Malaria, is not a viral disease but a parasitic disease caused by the Plasmodium parasite. It is transmitted through the bite of infected female Anopheles mosquitoes.

Option 4, Typhoid, is not a viral disease either but a bacterial infection caused by the bacterium Salmonella Typhi. It is usually spread through contaminated food and water.

It is important to note that while options 1, 3, and 4 are not viral diseases, they are still significant health concerns and can have serious consequences if left untreated.