It is tricky to explain things to people and not be confused in the process. So I now use the technique of guiding people by comparing things that are known to make them understand the unknown.
Here is how I explain how infection spreads -
Paaduka - Madhura kku ennAla dhaan odambu serilla (Madhura got sick because of me)
S atthai - eppadi ? (how?)
Paaduka - enakku fever irundadhu. ear infection irundadhu. naan dhaan Madhura kku kuduthen (I had fever and also ear infection and I gave the infection to Madhura)
S atthai - how did you give? kai aala ya ? (With your hands?)
Paaduka - (how do I explain this to her? I have to speak her language?)
S atthai - Do you know how you gave to her ?
Paaduka - naan onakka email anupicchA onakku varum dhaane. kai aala kudukka vendam, parka mudiyaadhu aana onakku kadaikum. (If I send an email, you receive it, right? I do not give the mail by hand and you cannot see it.)
Paaduka - adhu madhri dhaan naan Madhura kku fever kuduthen.
S atthai - (smiles) kids now a days !
