Brief Answer:
Probably viral gastroenteritis

Detailed Answer:
Hello and welcome to Ask A Doctor service.

I have reviewed your query and here is my advice.

It seems to be viral gastro-enteritis as it has followed a flu. Chronic got issues could be from low gut immunity and unclean water/food. It does not seem related to malabsorption from some food.

Complete stool examination can help in diagnosing the chronic problem.
Please let me know the medicines etc that you have tried. Also let me know if you have any other symptoms like constipation, fever, etc.

For the acute condition, it is better to fast (eat/drink nothing) for few hours. Also let me know if fasting helps with diarhea or not. If you cannot fast completely, then take fruit only like banana or pomegranate seeds.
Since you are passing stools very often ORS may also induce motions. If it is not inducing motions, then drink ORS in clean water with low TDS.
Antibiotics maynot help in viral but can be tried.

Hope this helps. Let me know if I can assist you further.
Dr Vaishalee

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