Similar to the production of circulating Epo (reviewed by [21]), hypoxia also increases Epo production and release in the nervous system, but various other challenges or insults have also been demonstrated to induce Epo in the nervous system, such as mechanical damage [22,23], infection [24], metabolic stress [25], elevated temperature [26], intense neural activity [27,28] and enriched environment [29]. Here, EPO is linked to infection.