El Niño could leave Lima without drinking water and increase the risk of digestive, respiratory and skin diseases

Another mechanism is related to animals. Flooding can displace rodents from their burrows and carry their urine into surface water. This contamination can favor the transmission of leptospirosis, a febrile illness that can present serious symptoms.

The fourth factor is social. “Overcrowding in shelters as a result of the structural damage caused by El Niño can increase respiratory and diarrheal diseases,” explains López Revilla.

But not all these risks present themselves in the same way. A flood or landslide generates a different scenario than a prolonged interruption of drinking water.

“The difference must be made clear: flooding is not the same as running out of water. In a flood or landslide, many people can be exposed simultaneously and for a short period to potentially contaminated water. Therefore, what dominates are leptospirosis, injuries and diarrhea,” he says.

However, a prolonged water outage works differently. “There is no dirty water that makes people sick, there is an absence of clean water that prevents washing hands,” explains López Revilla. Transmission can be maintained for longer periods of time through contact between people and surfaces.

And a second consequence appears: the storage of water.

“Then, the Aedes mosquito appears, because people need to store water, and it works as a breeding ground,” he warns.

This difference is especially important for Lima. The researcher maintains that the scenario that should receive the most attention is not necessarily a massive flood in the city, but an eventual interruption of supply.

The problem may originate outside the capital. “For that to happen, it doesn’t need to rain in Lima: it just needs to rain hard in the upper basin of the Rímac,” he explains, “The mud that descends down the river could force La Atarjea’s operation to stop and leave the city without water.”

For Walter Mendoza de Souza, senior researcher at the same university and specialist in statistics and public health, this scenario must be analyzed considering how long the emergency lasts and which areas of Lima are affected.

Vulnerability is not the same for the entire city. About a quarter of the Lima population lives on hillsides, where access to water already has restrictions in coverage, quality and opportunity, warns Walter Mendoza

“If ‘under normal conditions’ your access to water is already restricted in coverage, quality and opportunity, in the coming months the situation may be even worse.”

The researcher points out that interruptions in basic services can favor the increase in digestive, respiratory and skin diseases, especially when access to prevention, diagnosis and treatment services is limited.

The problem, however, does not end in homes. A prolonged interruption can directly compromise the response capacity of the health system.

“Without water there is no hand washing, no sterilization of instruments, no hemodialysis, no cleaning of environments,” warns López Revilla. “A prolonged outage not only makes the population sick: it compromises the ability of the health system to care for them.”

Mendoza adds another dimension: during an El Niño event, damage to infrastructure, transportation and communications can make it difficult for patients to reach facilities and for healthcare personnel to travel.

In emergencies of this type, other essential services may also be affected. Access to medications and vaccines, conservation of supplies, and care for patients with chronic diseases require specific contingency plans.

Given this scenario, both specialists agree that health surveillance should not focus solely on counting cases of dengue, leptospirosis or other diseases.

López Revilla proposes prioritizing measures such as guaranteeing a minimum amount of water per person and per day in the affected areas, keeping storage containers covered and ensuring water contingency plans for hospitals and health centers.

It also proposes monitoring residual chlorine at the point where people actually consume the water and not only at the exit from the treatment plant.

Mendoza, for his part, suggests that monitoring must integrate epidemiological and climatic information and consider not only infectious diseases, but also mental health, the availability of medicines and vaccines, and effective access to health services.