Investigating an Upsurge of Acute Encephalitis Patients at a Tertiary Hospital in Bogura, Bangladesh

<i>Background:</i> Japanese encephalitis (JE), Nipah virus encephalitis and some other viral encephalitis are endemic in northern districts of Bangladesh. Occasionally upsurge of hospital admission of encephalitis patients are reproted in the tertiary care hospitals which needs evaluation. In May 2015, Shahid Ziaur Rahman Medical College Hospital (SZMCH) in Bogura, Bangladesh, reported an increased admission of encephalitis patients. Due to the endemic nature of viral encephalitis in the region, including Japanese encephalitis (JE) and the Nipah virus, the hospital authority reached out to the Institute of Epidemiology, Disease Control and Research (IEDCR). <i>Objectives:</i> The investigation was performed to verify whether the event was an outbreak and to identify potential etiologies. <i>Methods</i>: A field investigation was conducted from June 2 - 5, 2015 in SZMCH. Hospital admission in Medicine wards from January 2014 to May 2015 were analyzed to determine baseline trends. A suspected encephalitis case was defined as any patient with acute onset of fever and unconsciousness or altered mental status, seizure, or other neurological symptoms. We interviewed the attendants of encephalitis patients admitted from June 3 - 4, 2015. Serum and cerebrospinal fluid (CSF) samples were collected and tested for JE virus IgM antibodies at IEDCR. Clustering and geographic distribution were assessed using an epidemic curve and mapping of cases by district. <i>Results:</i> A total of 17 suspected encephalitis cases were identified (mean age 37 years; 70% male; 41% mortality). The rate of encephalitis admissions in May 2015 (5.9/1000 hospital admission in Medicine wards) was not significantly higher than the baseline period (7.1/1000 hospital admission). No spatial or temporal clustering was observed. Four patients met the probable case definition based on CSF findings. Of these, one tested positive for JE IgM antibodies; the rest were seronegative. No epidemiological risk factors for Nipah virus were found. <i>Conclusion:</i> We conclude that the encephalitis was sporadic and had no spatial and temporal relation with each other. However, a confirmed JE case reveals ongoing viral encephalitis transmission in northern Bangladesh. We recommend to strengthen hospital-based surveillance, improve diagnostic capacity for rapid detection, confirmation and control of the outbreak.