| It existed in Michigan between 1868 and 1874, but only in the latter year epidemically, and not to a very great extent. |
| The subsequent emergence of the virus from Africa appears to have begun as early as the 1960s and was characterized by a surprisingly low frequency of epidemically successful dispersal events. |
| Influenza is a highly contagious respiratory infection of viral origin, which occurs epidemically most frequently during winter months. |
| It cannot therefore be spread epidemically, any more than diabetes or gout. |
