PAST CLIMATE IMPACTS ON HEALTH IN NICARAGUA
As part of the CRM TASP, Altamirano and Guzmán (2012) studied the impacts of past climate patterns on diarrhoea, dengue and
leptospirosis. These are some of the most important diseases in Nicaragua and are expected to depend significantly on climate
conditions. The statistical analysis focused on the SILAIS, or health regions, of Managua, León and Chinandega, because of the
high prevalence of the three diseases in these areas. The authors looked at correlations of temperature and precipitation with the
number of cases of the three diseases, both on a monthly basis to detect seasonal patterns, and with annual data, to look at the
impact of specific events as well as possible longer-term trends.
Diarrhoea
The World Health Organization (WHO, 2012a) defines diarrhoeal diseases “as the passage of three or more loose or liquid stools per
day (or more frequent passage than is normal for the individual),” which leads to dehydration and loss of nutrition. Diarrhoea kills
1.5 million children worldwide every year and is the second leading cause of death in children under five years of age. Diarrhoeal
disease is caused by bacterial, viral and parasitic organisms that infect the body through contaminated food or water, or from person
to person. According to MINSA (2011), 264,848 cases of acute diarrhoea were reported in 2010 in Nicaragua. Of these, 99,469 cases
were reported in the SILAISs of Managua, León and Chinandega. This amounts to an increase in cases for these three regions of
around 50 percent compared with the 2000 to 2009 average (Altamirano and Guzmán, 2012).
Climate variables can have an important influence on the prevalence of diarrhoea. For example, at higher temperature levels, the
insects that carry bacteria reproduce more rapidly. Extreme rainfall can lead to contamination of water, which increases the breeding
ground for bacteria, viruses and parasites. Droughts can also reduce the amount of available clean water and thereby increase
human contact with contaminated water.
Dengue
Due to a global resurgence in recent years, dengue is now the most common mosquito-borne viral disease in humans, with an
estimated 50 million infections a year worldwide. It is mainly transmitted by the predominantly urban mosquito Aedes aegypti and
leads to flu-like illness or even dengue haemorrhagic fever, which can be lethal.
Climate conditions can influence the spread of dengue in several ways. Temperature levels affect the survival and speed of reproduction
of both the virus and the mosquitoes that carry it. At different stages of their life cycle, mosquitoes require temperatures of around
25° C to 32° C. Transmission can occur within a temperature range of around 14° C to 40° C. Higher temperatures can shorten the
time between the infection of the vector and the vector’s ability to infect someone. Water temperatures are particularly important,
as the mosquito larvae grow in water. In warmer water they tend to develop more rapidly but will be smaller as adults, and as a
result, they need to bite more often in order to feed themselves with blood. Rainfall, on the other hand, can have an effect on the
available breeding area. Both heavy rainfall and droughts can create pools of water where mosquitoes can reproduce and grow.
Water deposits in and around settlements are of particular importance for dengue, a predominantly urban disease (Altamirano and
Guzmán, 2012).
The number of suspected monthly dengue cases closely follows seasonal rainfall patterns. Based on monthly averages for the period
from 1993 to 2010 and applying a one-month lag between rainfall data and the number of cases, Altamirano and Guzmán (2012)
found a 78 percent, 89 percent and 93 percent correlation for Managua, León and Chinandega, respectively. While the analysis
cannot prove a causal relationship, this result strongly supports the hypothesis that periods of heavy rainfall increase breeding
pools for disease-carrying mosquitoes. The second-highest
peak on record occurred in 1998, when El Niño conditions initially brought warm and dry weather before Hurricane Mitch brought
devastating rains in October. In the month of October, 1,985 mm of rain fell in Chinandega. The year 2010, the last and highest peak
in dengue cases, was a very wet year, with one tropical depression and two storms and annual precipitation exceeding averages.
Leptospirosis
Leptospirosis is a bacterial disease that can cause high fever, severe headaches, muscle pain, chills, redness in the eyes, abdominal
pain, jaundice, haemorrhages, vomiting, diarrhoea and a rash. Humans contract it through water contaminated by urine from
infected rodents or other animals. It enters the human body through skin abrasions and the mucosa of the nose, mouth and eyes.
Although not well-documented, leptospirosis occurs worldwide and peaks in the rainy season in endemic regions (WHO, 2012a).
Bacteria need water or high humidity and temperatures between 20° C and 37° C. They survive best in standing water, ponds, swamps and lagoons, but die quickly under
dry conditions (Altamirano and Guzmán, 2012). Because transmission requires contaminated water, cases typically peak in the rainy
season, and the disease can reach epidemic dimensions during floods (WHO, 2012a).
A comparison of climate and health data shows that observations in Nicaragua are in line with expected patterns. Of the 8,952 cases
that were reported in the three SILAISs of Managua, León and Chinandega between 1996 and 2010, over 80 percent occurred in the
months of October and November, right after the peak of the rainy season. What is interesting about this disease compared with others is the fact that peaks are very
high, so that there appears to be an epidemic threshold that, if passed, leads to a rapid spread of the disease.
Malaria
Nicaragua’s ‘First National Communication to the UNFCCC’ (República de Nicaragua, 2001) looked at the impacts of climate change
on malaria. Higher temperatures are expected to increase the prevalence of malaria, because they increase the speed of reproduction
and growth of the mosquitoes that transmit the disease. Also, below a certain temperature, the mosquitoes don’t survive. Rainfall
can affect the prevalence of malaria in similar ways as for dengue, as the mosquitoes need standing waters for reproduction.
Heat-related issues
According to community consultations conducted by López et al. (2011), dry conditions often lead to an increased prevalence of
respiratory diseases, mainly from increased contamination of the air with dust. It is also worth mentioning the results of a study by
Delgado Cortez (2009), which looked at the impacts of heat stress on sugarcane farm workers, who are exposed to temperatures
of up to 34.5° C. The output of workers who didn’t drink at least six litres of water was almost one-third lower than that of workers
who did drink sufficiently. Apart from the occupational health risk for the involved workers, this highlights the economic damages
of climate-induced health stress.
Health impacts of Hurricane Mitch
ECLAC (1999) conducted a thorough impact assessment shortly after Hurricane Mitch struck Nicaragua in October 1998. They
looked at, among other things, social and economic impacts in the health sector. This detailed analysis offers insights into some of
the more complex direct and indirect consequences of extreme events for health:
- The main reported causes of morbidity were acute respiratory infections, acute diarrhoea-related disease, skin diseases, impetigo, conjunctivitis, and the resurgence of vector-transmitted diseases such as cholera, dengue and malaria.
- The destruction of the health infrastructure reduced the system’s response capacity at a time when demand was soaring.
- The high number of victims and displaced people and the destruction of water and sanitation infrastructure led to massive hygiene problems, which in turn facilitated the spread of respiratory and diarrhoea-related diseases as well as meningitis and dengue.
- Providing people with enough water and food in the emergency was difficult because of high demand and destroyed infrastructure.
- After the disaster, flooding, damming and landslides favoured the creation of new sites prone to the generation of vectors, which has caused increases in cases of leptospirosis, rabies, Chagas’ disease and leishmaniaiasis, along with acute respiratory
- infections and diarrhoea-related diseases.
- Total economic losses caused by the hurricane were estimated at US$53 million, including direct damage to structures, equipment and installations and indirect costs stemming mainly from campaigns to combat hurricane-related diseases.
