Hi Melony! Hope you and your family are well during this hard times.
As you know, each country has their own issues with specific diseases. There are no other company as Genics, with worldwide disease databasis as you have - congratulations!
Each farmer have different timeline responses at the growout before shrimp starts dieing. Even between tanks or ponds contaminated with the same virus or bacteria. It´s quite common now, have positive results in some countries with considerable viral load, and the shrimp behave normally till harvest (excluding IHNNV of course, which could be considered present in nature, and eliminated from OIE list).
The advances in management and zootecnic response in the field, have been improve exponentialy after SPF programs and services as Multipath. But we still learning how the disease´s triggers works for each area and in each season, depending on water quality changes.
New virus strains will always come or get discovered, and mortalities are consequences from our management at the field - (yes, if someone stock the pond with positive WSSV larvae at the farm, knowing the temperature forecast will be cold, it´s farmers/technicians fault, not the environment).
I think the answer for your question is looking for the triggers, but not basics ones like pH, oxygen, temperature or alkalinity. One of the top list one, must be the bacterial community screening for the water/soil - not a specific ones like vibrio or bacilus genus only but a full family bacteria screening at the water and soil if applicable, as some companies are doing in Asia. With a regular screening test you will be able to see when and where the bacterial comunity dynamics change, improving our management to avoid mortality and keep the shrimps growing. Virus don´t kill the shrimp, the bacteria, other infections, or improper management does.
Some farmers will say, "oh we use probiotic/prebiotic/antibiotic/organic acid/essential oil, and we don´t have problem with that"...
But what is the point of products application if we don´t have informantion´s to see what changes at the culture unit, and how we are interfering at the ecosystem to potentialize the triggers or not? I think we have a lot to learn and research yet before say we know to rase shrimp, and bacteria screening is the fundamental source for this...
Sorry for an extense text and I hope this can help you, Fabio