Table 1.

Selected articles for the study and main findings

Year	Author	Journal	Study design	Main finding
2007	Borgherini et al.	Clin Infect Dis	Cross-sectional	Study of 157 patients with acute CHIK, showed that 52 of them had diabetes mellitus (DM) as comorbidity. Most of them were over 45 years of age, of these, 41% required hospitalization due to worsening of the viral infection, giving a significant higher rate of hospitalization OR (p = 0.008, OR 2.8 CI 1.32–5.94)
2009	Economopou-lou et al.	Epidemiol Infect	Cross-sectional	The study included 610 cases with an incidence rate of atypical CHIK 112/100,000 inhabitants, of whom 89% had associated comorbidities. DM was the second most reported comorbidity (39%). Further the results also showed that, of the total cases, 131 patients presented glycemic imbalance and 27 (20%) of them were diagnosed with DM for the first time. Of the 147 severe atypical cases with neurological disorders, 24% were diabetic. And those patients with severe cardiac conditions (n = 226), 48% had diabetes. Patients aged 40–60 years had a 2.5-fold higher risk of developing atypical forms of CHIK, while older patients 60 years and above had 1.6-fold higher risks in addition
2009	Staikowsky et al.	PLoSOne	Prospective	Patients with acute CHIKV were divided into two groups: active viremia and no viremia. It was observed that patients with active viremia had more comorbidities, mainly DM = 44/180 (24.4%) as compared to 8/34 (33.3%) without viremia. Female patients had frequent comorbidities (p < 0.05) as opposed to male patients. It was also observed that patients who required hospitalization were older and had more comorbidities (p < 0.001)
2009	Tandale et al.	J ClinVirol	Prospective	The study described cases of CHIK patients in two cities classified as classic, severe, and severe with neurological damage. Of 149 patients, DM was present only in severe cases (4/25) and in severe cases with neurological damage (4/10 and 15/59)
2009	Sissoko et al.	PLoSNeglTropDis	Restrospective cohort	The search for rheumatic manifestations in patients with CHIK were followed retrospectively. The results showed that of 147 patients confirmed with CHIKV, 32 had DM as comorbidity (OR 2.3, 0.9–5.3). In addition, the study showed that 84 patients remained with symptoms of rheumatic arthritis. Comorbidity was more common in these patients (OR 3.0, 1.5–5.9)
2012	Couturier et al.	Rheumatology	Prospective cohort	This was a prospective cohort analysis of the quality of life of patients with CHIK. Results showed that of 377 patients, 227 (60%) had associated comorbidities, OR 0.71 (0.57, 0.88), p > 0.002. Of these, 23 had DM
2015	Tolokh et al.	Am. J. Trop. Med. Hyg	Case report	Case report of a 50-year-old Puerto Rican man with diabetes with acquired acute Chikungunya virus infection. The patient evolved with atypical characteristics and severe manifestations such as leucopenia, thrombocytopenia, increased glycemic levels and ketone bodies, hepatic enzyme alterations, which culminated in the developmentof the diabetic ketoacidosis
2016	Crosby et al.	Int J Infect Dis	Cross-sectional	In a cross-sectional study of 65 patients with severe CHIKV admitted to Intensive Care Units, 54 had comorbidities (83%); DM wasthe second most prevalent comorbidity (32%). The study also showed that most diabetic patients did not have classic symptoms of Chikungunya, but may hadmore severe forms of the disease (p = 0.01)
2016	Jean-baptiste et al.	Am. J. Trop. Med. Hyg	Cohort	The only study that showed a direct relationship of DM in hospitalized patients with CHIKV, in the acute phase of the disease. It was found that diabetic patients worsened CHIK condition (p < 0.002) and presented greater arthralgia, fever and myalgia than non-diabetic patients (p < 0.008). Only diabetes was identified as a significant contributor to the presence of the triad of arthralgia, fever and myalgia (p = 0.002), time to improve arthralgia (p < 0.001) and duration of fever (p = 0.002). Diabetic patients had longer hospital stay (p < 0.0001) and a mean increase in glycaemia of 26.8% (p < 0.0001) when compared to baseline. Forty percent of diabetic patients required adjustment of the drug dose during the course of infection
2016	Perti et al.	Plos	Cross-sectional	The study reported that of 180 patients with CHIK, 71 had DM, and these patients had a higher risk for hospitalization, due to worsening of the condition (RR: 1.53; CI 95% 1.15–2.03). When adjusted for age the risk was 1.39 (1.06–1.84) (p = 0.02)
2016	Rollé et al.	EmergInfectDis	Cross-sectional	Diabetes mellitus was the most cited comorbidity in patients with severe CHIK 16/42 and non-severe CHIK 28/68