Wednesday 19 February 2014, 1-2pm
Speaker: Derek Gatherer, Health and Medicine
Location: Training room 2, Gordon Manley Building
Bayesian phylogenetic analysis of avian influenza A virus demonstrates that the “most recent common ancestor” (MRCA) existed approximately 1000 years ago. Most of the bifurcations within the phylogenetic tree occurred within a time window that can be dated with 95% confidence to the years 1366–1932 AD. This subtype diversification episode is temporally congruent with the ‘‘Little Ice Age”, a period of climatic cooling over the northern hemisphere. Furthermore, Bayesian probability mean ages indicate two bursts of diversification from 1672 to 1715 and from 1825 to 1868. The first of these follows in the wake of the coldest epoch in the Little Ice Age (the Maunder Minimum), and the second overlaps a later cooling episode (the Dalton Minimum). Since climate change is known to affect migration patterns in the reservoir host of influenza A, the aquatic wildfowl, and allopatric cladogenesis following population disruption is well supported in the evolutionary literature, a mechanism is proposed linking the Little Ice Age to influenza subtype diversification via ecological disruption of the wildfowl annual cycle. The suggestion that past climate change has impacted on influenza evolution implies that current global warming may cause a further burst of influenza subtype diversification with possible serious epidemiological consequences becoming apparent in the 22nd and 23rd centuries.