About the Plaga's Weakness (プラーガの弱点について), known as Irving's Note on Las Plagas in the English localization, is a file that can be found in Resident Evil 5.
The file can be found on the inside a building on the mining area, where Chris Redfield and Sheva Alomar encounter Ricardo Irving before being taken by the "Hooded Lady / Bird Lady", during Chapter 2-2.
IRVING'S NOTE ON LAS PLAGAS
Looks like a message...
Las Plagas → Possible mutation in the body
Low probability but evidence is compelling.
Possible sales point?
Weak against bright light.
Address problem immediately!!
プラーガ → 体内で変異？