The virus has been identified in the pulmonary nodules of African elephants as far back as the 1970s.[6] The first recognised fatal case of EEHV in an Asian elephant was identified at the National Zoo in Washington, D.C., in 1995;[20] testing on stored tissue samples was able to identify a number of earlier deaths as being due to the same virus. These cases have so far been identified as early as 1983.[2] Since this date, there have been a total of 54 more cases in North America and Europe, nine of which were successfully treated.[2] The May 2009 deaths of two calves at Whipsnade Zoo were not included in this calculation. This gives a fatality rate of over 80% among known symptomatic disease cases.