Assessing Reportable Disease Incidence Following Hurricane Sandy, New York City, 2012

BACKGROUND: The arrival of Hurricane Sandy in New York City on October 29, 2012 caused localized flooding and prolonged power disruption. The risk of infectious diseases may have been affected by floodwater exposure, shelter residence, overcrowding, and lack of refrigeration or heating. For 42 reportable diseases that could plausibly have been affected by hurricane-related exposures, we assessed whether hurricane-affected areas had higher disease incidence than other areas within NYC.

METHODS: We identified “post-hurricane” cases as confirmed, probable, and suspect cases with onset or diagnosis between October 30 and November 26 that were reported via routine passive surveillance as of December 13, 2012. “Pre-hurricane” cases for the same 4-week period were identified in 5 prior years, 2007-2011. Cases were geocoded to the census tract of residence. The NYC Office of Emergency Management determined (1) the proportion of the population in each census tract living in a flooded census block and (2) the subset of flooded tracts severely “impacted” by prolonged service outages. A separate multivariate regression model was constructed for each disease, modeling the outcome of case counts using a negative binomial distribution. Independent variables were: neighborhood poverty; whether cases were pre- or post-hurricane (time); the proportions flooded in impacted and not impacted tracts; and interaction terms between the flood/impact variables and time. Models used repeated measures to adjust for correlation of cases within a tract and an offset term of the log of the population size. Sensitivity analyses assessed the effects of including pending cases and of accounting for variations in reporting volume (e.g., due to facility closure) by using an offset term of the log of total cases.

RESULTS:  Legionellosis was the only disease in primary or sensitivity analyses with positive and statistically significant (p<0.05) interaction terms, indicating that more severely flooded areas had more cases post-hurricane, adjusting for baseline differences (p=0.01 in impacted areas, p=0.02 in not impacted areas). However, there were only 3 legionellosis cases post-hurricane, in areas that were: not flooded (n=1), flooded/not impacted (n=1), and flooded/impacted (n=1).

CONCLUSIONS: Hurricane Sandy did not appear to elevate reportable disease incidence in NYC. Defining and acquiring reliable data and meta-data regarding hurricane-affected areas was a challenge. Relevant metrics could be developed during disaster preparedness planning. These methods to detect excess disease can be adapted for future emergencies.