Chronic pain associated with the Chikungunya Fever: long lasting burden of an acute illness

BACKGROUND Chikungunya virus (CHIKV) is responsible for major epidemics worldwide. Autochthonous cases were recently reported in several European countries. Acute infection is thought to be monophasic. However reports on chronic pain related to CHIKV infection have been made. In particular, the fact that many of these patients do not respond well to usual analgesics suggests that the nature of chronic pain may be not only nociceptive but also neuropathic. Neuropathic pain syndromes require specific treatment and the identification of neuropathic characteristics (NC) in a pain syndrome is a major step towards pain control. METHODS We carried out a cross-sectional study at the end of the major two-wave outbreak lasting 17 months in Réunion Island. We assessed pain in 106 patients seeking general practitioners with confirmed infection with the CHIK virus, and evaluated its impact on quality of life (QoL). RESULTS The mean intensity of pain on the visual-analogical scale (VAS) was 5.8 +/- 2.1, and its mean duration was 89 +/- 2 days. Fifty-six patients fulfilled the definition of chronic pain. Pain had NC in 18.9% according to the DN4 questionnaire. Conversely, about two thirds (65%) of patients with NC had chronic pain. The average pain intensity was similar between patients with or without NC (6.0 +/- 1.7 vs 6.1 +/- 2.0). However, the total score of the Short Form-McGill Pain Questionnaire (SF-MPQ)(15.5 +/- 5.2 vs 11.6 +/- 5.2; p < 0.01) and both the affective (18.8 +/- 6.2 vs 13.4 +/- 6.7; p < 0.01) and sensory subscores (34.3 +/- 10.7 vs 25.0 +/- 9.9; p < 0.01) were significantly higher in patients with NC. The mean pain interference in life activities calculated from the Brief Pain Inventory (BPI) was significantly higher in patients with chronic pain than in patients without it (6.8 +/- 1.9 vs 5.9 +/- 1.9, p < 0.05). This score was also significantly higher in patients with NC than in those without such a feature (7.2 +/- 1.5 vs 6.1 +/- 1.9, p < 0.05). CONCLUSIONS There exists a specific chronic pain condition associated to CHIKV. Pain with NC seems to be associated with more aggressive clinical picture, more intense impact in QoL and more challenging pharmacological treatment.