A terrible earthquake has just occurred in Turkey and Syria on February 6, 2023. It seems that the death toll is now over 41,000.
What is it about?
While more than 26 million people are potentially affected, the WHO considers that more than 5 million of them are particularly vulnerable (elderly, children…). We now fear the spread of outbreaks: what is the link between earthquakes and outbreaks?
Earthquakes are the most common natural disaster. Generally unpredictable, an earthquake lasts only a few seconds, but the consequences are devastating, with thousands of people usually killed under the collapse of their houses. In addition, infrastructure, such as water supply, is damaged, seriously altering the hygiene conditions of the survivors.
What is an earthquake?
Let’s take the opportunity to give some notions about earthquakes.
The earth’s crust is composed of fifteen major and 40 minor plates, floating on a liquid layer of magma.
All these plates move from 1 to 20 centimeters per year in different directions by forming zones of divergence (the plates move away from each other), of subduction (while approaching a plate slides under another), of collision (the part between the 2 plates rises while forming mountains) and of sliding (the plates slide one with respect to the other by a transverse movement)
The point where the plates meet, several kilometers down, and where the earthquake occurs is known as the source or “hypocenter” of the earthquake. The epicenter is the point corresponding to the hypocenter located on the surface of the earth, where the earthquake is strongest.
The main shock is usually preceded by smaller shocks, which nevertheless emit vibrations in all directions and should alert people when detected.
The main shock is generally followed by more or less important “aftershocks”: they correspond to the rearrangements and the stabilization of the various plates.
An earthquake is characterized by the calculation of its magnitude from the waves detected by seismographs. An earthquake of magnitude 5 corresponds roughly to the energy released by the nuclear bomb that destroyed Hiroshima. The highest magnitude earthquake occurred in Chile in 1960 with a magnitude of 9.5 on the Richter scale of 9.
Magnitudes are logarithmic, an earthquake of magnitude 7 is ten times stronger than an earthquake of magnitude 6 and 100 times stronger than an earthquake of magnitude 5. Earthquakes of magnitude 3 are perceptible by the population.
The earthquake in Turkey and Syria on February 6, 2023
The epicenter of these earthquakes is located in a geologically active area near the Maraş triple junction formed by the intersection of the African, Anatolian, and Arabian plates (see diagram).
A first tremor occurred at 1h 17 min 36 s (UTC) with a magnitude of 7.8 and a depth of 17.9 km. A second earthquake occurred 9 hours later with a magnitude of 7.5 to 7.7, but at a depth of only about twenty kilometers. This was followed by multiple aftershocks (at least 120).
The main health effects
Simple hygiene measures are no longer guaranted
The corpses under the rubble are decomposing and the smell is getting worse every day. The morgues are no longer sufficient. The corpses wrapped in simple bags are waiting to be buried in mass graves dug in a hurry.
The garbage is piling up, the survivors are living in the street, without water or functional toilets. Without heating, they fall ill because of the cold and there is no medicine to treat them. Often it is the food that is missing.
The consequences on the health of the population are very numerous
Trauma and injuries
On considère que 75 % des traumatismes sont dus à l’effondrement des bâtiments. Les blessés coincés sous les gravats ne survivent pas longtemps sans eau ni nourriture. Cependant, au cours de ce récent séisme des personnes vivantes ont été sauvées plus de 13 jours après le début de la catastrophe. Sous les décombres, les personnes souffrent de plaies non soignées qui peuvent s’infecter, de fractures, et leurs muscles compressés peuvent souffrir du « crush syndrome » qui se manifeste par des dysfonctionnements rénaux.
Diarrheal diseases
Disruption of drinking water supplies and destruction of sanitation facilities lead to poor hygiene practices. Bacteria and other enteric viruses cause diarrhea, which is rapidly transmitted due to overcrowding and lack of sanitation.
Specifically, when cholera is prevalent in an area, close attention should be paid to its possible reappearance after an earthquake. In Pakistan, shigellosis may also be a specific problem.
Respiratory and skin diseases
Massive population displacements and overcrowded communal emergency shelters are the sources of respiratory and skin diseases. As routine health services are no longer functioning, vaccinations are no longer provided and the transmission of infectious diseases is all the more likely. This is particularly true for measles in regions where vaccination is not sufficiently practiced and which risks spreading rapidly due to promiscuity.
Vector-borne diseases
Sanitation services are no longer functioning, waste accumulates, and mosquitoes proliferate in stagnant water, leading to increased transmission of dengue, chikungunya and/or malaria. But it must be emphasized that these outbreaks will only occur in areas where they exist prior to the earthquake. By proliferating, rats in contact with humans increase the incidence of leptospirosis.
General health
As there is no more care structure, there are no more stocks, therefore no more infant care requiring specific material: infant formula, diapers… Moreover, the follow-up of chronic diseases is no longer assured.
For survivors, the priority in terms of public health must be access to decent shelter, clean water and care.
Risk of outbreak
It should be remembered that corpses do not carry contagious diseases. They do not represent an outbreak threat in this type of context. However, their removal is necessary because of the odors and the negative psychological aspect they generate. Not to mention that rats can also play a role in the transmission of leptospirosis!
There is always a fear after an earthquake (or any other natural disaster like a tsunami) that outbreaks will occur. But, as we have just seen, the risks of outbreaks are not directly linked to the earthquake. Isolated outbreaks can occur (cholera, dysentery, measles, dengue, malaria…) but they result from the precarious living conditions in the destroyed areas and these outbreaks only exist if the disease was already present before the disaster. However, epidemiological surveillance is essential to ensure that isolated outbreaks do not become generalized outbreaks.
However, cholera has been known to occur in Syria since August 2022. The disease is favored by the lack of clean water and sewage system, so it will be necessary to closely monitor the emergence of possible cases. The same is true for Salmonella Typhi, responsible for typhoid fever, Shigella and Campylobacter (agents of dysentery) which proliferate in water contaminated by human waste.
A particular case, that of cholera after the 2010 earthquake in Haiti
The 2010 earthquake in Haiti is an earthquake of magnitude 7.0 to 7.3 that occurred on January 12, 2010. While no case of cholera had been reported for a century, an outbreak occurred 6 months after the earthquake: it caused 10,000 deaths mainly in Haiti and the Dominican Republic but also in Cuba and Mexico. It turned out that the bacterium, Vibrio cholerae, had been imported by Nepalese “blue helmet soldiers”, healthy carriers of the disease that was raging in their country at the time and in the United Nations Stabilization Mission in Haiti. This outbreak spread suddenly in the country, favored by the promiscuity and the precarious sanitary conditions after the earthquake.
The two events, the earthquake and cholera outbreak, even if they are linked in our mind, are completely independent, the bacteria having been brought in well after the earthquake but has been able to proliferate rapidly because of the not yet restored hygiene conditions.
Conclusion
There is no direct link between “earthquake and outbreak” but degraded hygiene conditions allow the amplification of respiratory and dysenteric diseases in particular. On the other hand, if there are pre-existing outbreaks, such as cholera, bacillary dysentery or vector-borne diseases such as malaria, the degraded hygiene conditions may amplify them.
(186)
Autor: Prof. François Renaud