A - organism

- A actinomycetemcomitans - A baumannii - A catonensis - A celatus - A costaricensis - A faecalis - A hydrophilia - A israelii - A lumbricoides - A marginale - A phagocytophilum - A pleuropneumoniae - A salmonicida - A vaginae - Acanthamoeba - acid fast bacteria (AFB) - Acinetobacter - Acinetobacter baumannii - Actinobacillus actinomycetemcomitans - Actinobacillus pleuropneumoniae - Actinomyces - Actinomyces israelii - Actinomycetes - adenovirus - Adlercreutzia equolifaciens celatus - Adlercreutzia equolifaciens subsp. celatus - Adlercreutzia equolifaciens subspecies celatus - Aedes - Aedes aegypti (Asian tiger mosquito) - Aedes albopictus (Asian tiger mosquito) - Aeromonas hydrophilia - Aeromonas salmonicida - AFB - Afipia felis - African eye worm - African sleeping sickness Trypanosoma - African trypanosoma - African tumba fly - Aggregatibacter actinomycetemcomitans - Aggregatibacter pleuropneumoniae - Akkermansia - Alcaligenes faecalis - Amblyomma americanum - Amebae - amoeba - Amoebae - Amoebida - Anaplasma - Anaplasma marginale - Anaplasma phagocytophilum - Ancylostoma duodenale (hookworm) - Angiostrongyliasis due to Angiostrongylus cantonensis - Angiostrongyliasis due to Angiostrongylus costaricensis - Angiostrongylus cantonensis - Angiostrongylus costaricensis - Anopheles - anoplura - Arachnia - arbovirus - Arcanobacterium (Corynebacterium) hemolyticus - arenaviridae - arenavirus - Arroyo virus - Arroyovirus - Asaccharobacter celatus - Ascaris - Ascaris lumbricoides - Asian longhorned tick - astrovirus - Atopobium vaginae - Atracidae - Avian flu - avian influenza A