Mu ntangiriro za 2009, mu gihugu cya Mexico no muri Leta Zunze Ubumwe za Amerika, hatangiye kugaragara abarwayi bafite ibimenyetso bidasanzwe bya gripo. Iyi ndwara yaje kwemezwa ko iterwa na virusi nshya ya gripo yiswe A(H1N1), ituruka ku moko atandukanye y’udukoko two mu ngurube, inyoni n’abantu (reassortment). Byagaragaye ko iyi virusi yari ishobora kwandura mu bantu vuba kandi ikorohera gukwirakwira, ibintu byahise bihangayikisha inzego z’ubuzima ku isi hose.
Ku wa 11 Kamena 2009, Ishami ry’Umuryango w’Abibumbye ryita ku Buzima (WHO) ryatangaje ko icyorezo cya H1N1 cyageze ku rwego rwo hejuru rw’icyorezo mpuzamahanga (Phase 6 pandemic), nyuma yo gukwirakwira mu bihugu birenga 70. Nubwo ubukana bwayo butari hejuru cyane nk’ibindi byorezo nka Ebola, ubushobozi bwayo bwo kwandura byihuse bwatumye ihabwa agaciro gakomeye. Iri tangazo ryari irya mbere kuva mu 1968, igihe gripo ya Hong Kong nayo yari yateye isi.
Muri Amerika gusa, hagati ya Mata 2009 na Mata 2010, hatangajwe abarwayi barenga Miliyoni 60.8. Abarwayi bajyanywe mu bitaro 274,000, naho abapfuye 12,469. Ku isi hose, WHO yemeje ko abapfuye bashobora kuba bari hagati ya 151,700 na 575,400. Uko igihe cyagiye gihita, habonetse imiti yifashishwa nka Oseltamivir (Tamiflu), ndetse hakorwa inkingo zatangiye gukoreshwa mu mpera z’umwaka wa 2009. Abantu bari mu byago byinshi (nk’abagore batwite, abarwayi ba asthma n’abafite indwara zidakira) bahawe agaciro k’imbere mu gukingirwa no kuvurwa byihuse.
Ku wa 10 Kanama 2010, WHO yatangaje ko icyorezo cya H1N1 cyarangiye ku rwego mpuzamahanga, ariko virusi yayo yakomeje gukwirakwira nk’igice cya gripo isanzwe (seasonal flu). Kugeza ubu, iyo virusi igaragara buri mwaka kandi inkingo za buri mwaka z’icyorezo cya gripo zishyirwamo H1N1. Isomo rikomeye cyasize ni uko ibyorezo bishobora gutungurana, bikaba byakomoka ku nyamaswa, bikadusaba kwitegura, gukora ubushakashatsi, no kugira uburyo buhamye bwo kugenzura no kwihutisha ingamba zo kwirinda no kuvura.