Epidemic retinitis and community outbreaks

PURPOSE: The objective of this study was to correlate seasonal variation of epidemic retinitis (ER) with concurrent community outbreaks. METHODS: This is a retrospective, observational, comparative study conducted in a tertiary care eye hospital in south India. Monthly variation in number of ER cases in comparison with reported community outbreaks by Integrated Disease Surveillance Program (IDSP) from 2009 to 2020 in the same region were studied. Month-wise graphs against number of patients were plotted for ER and for each community outbreak. RESULTS: ER was diagnosed in 163 patients. Diagnosis of presumed rickettsial ER was made in 48 cases (29.44%), chikungunya in 5, dengue in 3 and typhoid in 6 cases, while in other cases the etiological diagnosis remained uncertain (n = 101). Multiple positive serological tests were seen in 6 patients (Weil Felix Test (WFT) with WIDAL in 4 and chikungunya IgM with WFT in 2 patients). Relevant reported outbreaks by IDSP were: Pyrexia of unknown origin (PUO) (n = 5148), Chikungunya (n = 6577), Dengue (n = 7350), Measles (n = 1422), Mumps (n = 881), Rubella (n = 288), Malaria (n = 2262), Chicken Pox (n = 2385), Typhoid (n = 597), Kyasanur Forest Disease (n = 381), Scrub Typhus (n = 13), Typhus fever (n = 4), Japanese Encephalitis (n = 15). None of the outbreak graphs pattern was identical or similar to the graph of ER. Inverse relation of the graph of dengue outbreak with ER was observed. CONCLUSION: Inverse correlation between dengue and ER should be further studied for causation, which we believe may prove dengue as least common cause. Reporting of rickettsial outbreaks should be enhanced by undertaking statewide awareness and procurement of gold standard tests.