Vayiraasi

Kano kawuka kali mu ttuluba ly’obwo obumanyiddwa ng’obusirikitu akavaako endwadde kyokka nga keeyubulira oba okwalulira munda wa butoffaali (cell) obulamu obw’ekitonde ekirala(kwe kugamba nti ku lwako kokka, akawuka kano tekasobola kweyalula, kye kakola okweyalula, keegatta ku butoffaali bulala obulina obusobozi okweyaluza bwokka. Mu mbeera eno, buli akatoffaali kali lwe keeyalula, nga n'akawuka kano aka viyiraasi keeyalula.)
Olw'ensonga eyo gye tulabye waggulu,viyiraasi zisobola okukosa ebitonde by’obulamu eby’enjawulo omuli ebisolo, ebimera n’obuwuka obulala obwa bakitiiriya ne archea.

Okuva 1892 omusajja Dmitri Ivanovsky bwe yawandiika ng’annyonnyola ku kawuka akaali kakosa ekirime kya taaba okutuuka mu 1898, Martinus Beijerinck we yazuulira akawuka ka vayiraasi akayitibwa  mosaic virus, ebika bya vayiraasi nga 5,000 bizze bivumbulwa ne binnyonnyolwa.
Obuwuka bwa vayiraasi busangibwa kumpi mu buli mbeera eba amu obuluma ku nsi (ecosystem).

Essomo ku buwuka buno liyitibwa (virology) nga lino ttabi ku ssomo ku butonde (microbiology)