Perhaps you should try some spelling variations:
"decrease pathogen load" » "decrease pathogens load" (Expand Search), "decrease pathogen lead" (Expand Search)
"decreased pathogenic load" » "decreased pathogensic load" (Expand Search), "decreased pathogenic lead" (Expand Search), "decreased pathogens load" (Expand Search), "decreased pathogenesis load" (Expand Search)
"increase pathogen load" » "increase pathogens load" (Expand Search), "increase pathogen lead" (Expand Search)

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• Performing a fuzzy search may retrieve terms with similar spellings: (((("decrease pathogen load") OR ("decreased pathogenic load"))) OR ("increase pathogen load"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"decrease pathogen load\") OR (\"decreased pathogenic load\"))) OR (\"increase pathogen load\"))".
• Removing quotes may allow a broader search: (((( decrease pathogen load ) OR ( decreased pathogenic load ))) OR ( increase pathogen load )).
• Adding a wildcard symbol may retrieve word variants: (((("decrease pathogen load") OR ("decreased pathogenic load"))) OR ("increase pathogen load"))*.