Kwayoyin cuta suna ko'ina kuma sun mamaye miliyoyin shekaru. Babu wani nau'i na rayuwa da aka keɓe, musamman ba mutum ba. Daga AIDS zuwa SARS (= matsananciyar ciwo na numfashi), ta hanyar ƙanƙara ko hanta na C, cututtukan ƙwayoyin cuta sun lalata yawan jama'a kuma koyaushe suna tayar da yanayin bala'in lafiya. Wasu, duk da haka, sun fi kowa kuma ba su da illa ga lafiya.

Gaskiya "taurari" na hunturu, mura, gastroenteritis da sanyi na yau da kullum suna magana game da su a wannan lokaci na shekara. Matsakaicin kamuwa da cuta yana kaiwa ga tsari a wannan lokacin, wanda ke nuna sanyi da ƙarancin hasken rana. Amma wace rawa yanayin ke takawa wajen bullowar wadannan kololuwar annoba? Shin akwai ƙarin ƙwayoyin cuta a cikin iska? Shin jikinmu ya fi rauni?

Kafin amsa duk waɗannan tambayoyin, dole ne mu tuna yadda girman duniyar ƙwayoyin cuta take. Ba a sani ba har zuwa ƙarshen XIX^stkarni, har yanzu ya kasance ba a gano shi ba a yau, saboda rashin isassun albarkatun fasaha. A haƙiƙa, an yi ɗan bincike kan yanayin ƙwayoyin cuta na iska, da kuma yadda waɗannan ƙungiyoyi suke hulɗa da muhalli. Duk da haka, mun san cewa wasu ƙwayoyin cuta suna yaduwa ta hanyar iska, yayin da wasu kuma, hulɗa ce mai mahimmanci. Wannan a gaskiya ya bayyana ta kwayoyin halittar kwayar cuta.

Ainihin, duk suna da irin wannan yanayin aiki: kwayar cutar ta shiga jiki, ta shiga tantanin halitta, sannan ta saki kwayoyin halittar da ke cikinsa. Wannan abu sai ya tilasta wa kwayar halitta parasitized yin ɗaruruwan kwafin ƙwayoyin cuta waɗanda za su taru a cikin tantanin halitta. Idan akwai isassun ƙwayoyin cuta, suna barin tantanin halitta don neman wasu ganima. A nan ne za mu iya lura da babban bambanci tsakanin nau'ikan ƙwayoyin cuta guda biyu.