Risk factors for hospitalization of patients with chikungunya virus infection at sentinel hospitals in Puerto Rico.

Background: Hospitalization of patients during outbreaks of chikungunya virus has been reported to be uncommon (0.5-8.7%), but more frequent among infants and the elderly. CHIKV was first detected in Puerto Rico in May 2014. We enrolled patients with acute febrile illness (AFI) presenting to two hospital emergency departments in Puerto Rico and tested them for CHIKV infection to describe the frequency of detection of CHIKV-infected patients, identify risk factors for hospitalization, and describe patients with severe manifestations.

Methodology/principal Findings: Serum specimens were collected from patients with AFI and tested by rRT-PCR. During May-December 2014, a total of 3,035 patients were enrolled, and 1,469 (48.4%) had CHIKV infection. A total of 157 (10.7%) CHIKV-infected patients were hospitalized, six (0.4%) were admitted to the intensive care unit, and two died (0.1%). Common symptoms among all CHIKV-infected patients were arthralgia (82.6%), lethargy (80.6%), and myalgia (80.5%). Compared to patients aged 1-69 years (7.3%), infant (67.2%) and elderly (17.3%) patients were nine and two times more likely to be hospitalized, respectively (relative risk [RR] and 95% confidence interval [CI] = 9.16 [7.05-11.90] and 2.36 [1.54-3.62]). Multiple symptoms of AFI were associated with decreased risk of hospitalization, including arthralgia (RR = 0.31 [0.23-0.41]) and myalgia (RR = 0.29 [0.22-0.39]). Respiratory symptoms were associated with increased risk of hospitalization, including rhinorrhea (RR = 1.68 [1.24-2.27) and cough (RR = 1.77 [1.31-2.39]). Manifestations present among <5% of patients but associated with patient hospitalization included cyanosis (RR = 2.20 [1.17-4.12) and seizures (RR = 3.23 [1.80-5.81).

Discussion: Among this cohort of CHIKV-infected patients, hospitalization was uncommon, admission to the ICU was infrequent, and death was rare. Risk of hospitalization was higher in patients with symptoms of respiratory illness and other manifestations that may not have been the result of CHIKV infection.