Explaining rapid reinfections in multiple-wave influenza outbreaks: Tristan da Cunha 1971 epidemic as a case study

Camacho, Anton; Ballesteros, Sébastien; Graham, Andrea L.; Carrat, Fabrice; Ratmann, Oliver; Cazelles, Bernard

A swine-origin influenza A/H1N1 virus that arose in 2009 reminds us of the persistent risk of influenza pandemics. Lessons from the past are precious and may help us to anticipate and manage such potential disasters [1] . The most striking example is certainly the 'Spanish' influenza pandemic of 1918 -1919 that occurred in three waves and caused about 50 million deaths worldwide in only nine months [2] . To date, this multiple-wave outbreak pattern, which has also been reported during several other pandemic episodes, remains only partially understood. On one hand, there is evidence from the 2009 A/H1N1 pandemic that climate variations and school closing and reopening shape the timing of successive epidemic waves [3] . On the other hand, the explicit reports of individuals experiencing reinfections over a short time interval during pandemic seasons are still poorly understood [4 -7] .