Acute infectious disease associated with catastrophic climate events and global warming in Mexico

Based on our climate change modeling, average temperatures can be expected to rise, and pluvial precipitation can be expected to rise for most of the State of Nuevo Leon within the next 10 years. We found a remarkable rise in the incidence of transmissible infectious disease symptoms after Hurricane Alex. Gastrointestinal symptoms predominated and were associated with drinking water probably because of the contamination of clean water, the disruption of water sanitation, and the inability to maintain home hygiene practices. According to data from the “Centro Nacional de Vigilancia Epidemiológica y Control de Enfermedades”, the trend of rising temperatures and rainfall in the State of Nuevo Leon correlates positively with a rise in infections due to salmonellosis (50%), shigellosis (39%), typhoid fever (42%) and dengue (19%). Such epidemics after catastrophic events can be attributed to multiple factors including changes in human behavior, local climate, local biota and the availability of necessary human resources. All of these factors might alter the protective measures that normally prevent disease. Some of the affected people will gather in shelters with more abundant contagious pathogens, live with more stress and with less mobility. Common routes of transmission include the: respiratory-route, dermal-route, blood-borne diseases, and fecal-oral route. Some epidemics can lag after the event, such as with malaria, which can be seen with a lag time of 6-8 weeks after a flood.¹⁴ In 2000, a flood in Mozambique¹⁵ showed a 2-4 fold increase in the incidence of water-borne diseases. Our telephone survey data showed a similar 3.8 fold increase in the incidence of human infectious diseases after Hurricane Alex. Respiratory diseases are also associated with climate change. In 2010, the US-Mexican border region reported 387.3 cases per 100,000 inhabitants¹⁶ - an impressive 98.1% rise in the preceding 5-year period. This large increase in number of reported disease cases may be related to improvements in diagnostic capabilities in local facilities, but were likely also related to increases in pollution, pollen production, and climate change. Deterioration of normal preventive and hygienic measures, provoked by the flood, wind burst, and normal living practice might increase the possibilities to drink polluted water, decayed food, had less medical or pharmacological access and more contact with people with contagious disease. Greenhouse gases can contribute to air pollution. For example, naturally produced and manmade CO2 pollution is associated with an increase in pollen production. CO2 can function as a plant fertilizer, thereby promoting its growth, which along with the increase in global temperatures might also promote an increase in pollen producing plants and extend their growing period.¹⁷ Early and more prolonged exposures to pollen and other air pollutants might explain the rising trends of asthma.¹⁸ Hurricane Alex related flooding in Monterrey city produced substantial damage: 6 deaths attributable to food, more than 15,000 internally displaced persons, a substantial increase in disease rates, job absenteeism of greater than 50%, and an estimated economic loses of 1,296 million dollars. Due to the increasing risks associated with global climate change, including more frequent and more serious meteorological conditions that increase the risk of severe flooding, governments are obligated to produce better early warning systems, and new and better disaster readiness plans (including preparedness for more timely interventions that can prevent the early spread of diseases and more economic resources for the timely repair of damages.) Despite some progress of late, contingency countermeasures in our city will still need to improve in order to reduce the risks associated with flooding in different areas of the city. In 400 years of Monterrey’s history, we have had 19 floods; two per century in the first three centuries, seven in the twentieth Century, and another two in the first 10 year of our current century. Floods are a relative frequent event in the Monterrey metropolitan area, should be expected to become even more frequent as the climate changes. Public policy has a strong role to play in developing countermeasures that can address human health and human infrastructure damages, and reduce the risk to the larger population. This can be achieved by improving the levies in the Santa Catarina river bank, modernizing the municipal sewage and waste disposal systems, and the more timely provision of clean water and other needed services to the affected population.