ɪn sˈɛvɹəl flˈuː pˌɑːpjʊlˈeɪʃənz, ðə tˈaɪm tə ðə mˈoʊst ɹˈiːsənt kˈɑːmən ˈænsɛstɚ tˌiːˌɛmˈɑːɹsˌiːˈeɪ ʌv "sˈɪstɚ" stɹˈeɪnz, ɐn ˌɪndɪkˈeɪʃən ʌv ɹᵻlˈeɪɾᵻdnəs, sədʒˈɛstᵻd ðæt ðeɪ hæd ˈɔːl ɪvˈɑːlvd fɹʌm ɐ kˈɑːmən pɹoʊdʒˈɛnɪɾɚ wɪðˌɪn dʒˈʌst ɐ fjˈuː jˈɪɹz.
In several flu populations, the time to the most recent common ancestor (TMRCA) of "sister" strains, an indication of relatedness, suggested that they had all evolved from a common progenitor within just a few years.