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History and distribution
The earliest documentation concerns an epidemic of AHSV into the Middle East, in 1327. Later reports of AHS occurred following the introduction of horses into central and southern Africa during the seventeenth century.
Since modern age to nowadays, AHSV has become endemic in tropical and sub-tropical areas of Africa south of the Sahara. Just occasional excursions into North Africa or the Arabian Peninsula happened. However in the period 1959 to 1961 AHSV-9 expanded out of Africa and spread in a broad swathe across Saudi Arabia, Syria, Lebanon, Jordan, Iraq, Turkey, Cyprus, Iran, Afghanistan, Pakistan and India.
During 1965 AHSV-9 again spread beyond its sub-Saharan endemic zones and appeared first in Morocco then spreading into Algeria and Tunisia before crossing to Spain, in October 1966. The appearance of AHSV in North Africa was thought to be due to the movement of nomads.
In July 1987 an outbreak of AHS due to serotype 4 of the virus was reported in central Spain. The outbreak was apparently caused by the importation of a number of sub-clinically infected zebra from Namibia. The virus had persisted in the area for at least five years overwintering four times in the process; and further more severe outbreaks occurred in Spain during 1988, 1989 and 1990, in Portugal in 1989 and in Morocco in 1989, 1990 and 1991.
In February 2020 the first AHS outbreak in Thailand caused by serotype 1 was reported to the OIE, affecting 191 equines and causing 175 deaths.
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