Post-disaster communicable disease surveillance and response plan

Flooding in the rural districts of Bagmati Province creates the classic postdisaster conditions for communicable disease transmission: contamination of drinking-water sources, destruction of latrines, displacement of populations into crowded temporary shelters, interruption of health services and cold chain, expansion of vector breeding habitat, and loss of livestock with associated zoonotic exposure. Floods do not import new pathogens; they amplify the pathogens already endemic in the area. Preparedness must therefore be built on what is known to circulate in Bagmati Province — including the enteric pathogens Vibrio cholerae O1, Salmonella Typhi and hepatitis A and E viruses, together with dengue virus, Orientia tsutsugamushi, Leptospira species, Japanese encephalitis virus, measles virus, and residual foci of malaria and visceral leishmaniasis.

Two operational realities shape this plan. First, the interval between exposure and detectable clusters is short for enteric disease (2–14 days) and long for vector-borne and leptospiral disease (2–8 weeks), so surveillance intensity must be sustained well beyond the point at which media and political attention recede. Second, the routine surveillance system will be degraded exactly when it is most needed, because reporting health facilities may be damaged, staff displaced and connectivity lost. Apparent declines in reported cases in the first weeks after a flood are more often artefacts of reporting failure than evidence of control.