COVID-19 infection rates would rise if a large earthquake occurred during the pandemic. Researchers say that the number of resulting new cases depends on whether authorities prepare now.
By Elizabeth Goldbaum, Science Writer
Citation: Goldbaum, E., 2020, Preparing for an earthquake during a pandemic, Temblor, http://doi.org/10.32858/temblor.117
Right after a magnitude-5.3 earthquake hit Zagreb, Croatia, on March 22, 2020, Vitor Silva reached out to his colleagues in the shaken city. “Did the number of COVID-19 cases increase?” he asked them.
The earthquake left piles of rubble in the city’s downtown, damaged approximately 250 homes, and forced 59 people to seek temporary shelters. Before the event, there were 87 COVID-19 cases in Zagreb. In the following two weeks, 337 more cases were reported in the city.
The jump in cases after this moderate earthquake was relatively low in part because there were few preexisting cases and the government enforced timely, strict social distancing regulations, Silva, a risk coordinator with the Global Earthquake Model Foundation in Pavia, Italy, said.
“However, we will likely live with COVID-19 for another year or more and it’s important to understand and prepare for a potentially larger earthquake,” Silva said. Silva and his colleague Nicole Paul, a disaster risk analyst at the same organization, studied the aftermath of the Croatian and other earthquakes to quantify the potential impact that seismic events can have on viral infection rates.
They created a model to help forecast future scenarios and found that for a test case focused on Portugal, if the aftermath of an earthquake is managed quickly and efficiently, there would be a negligible increase in COVID-19 cases. If a large earthquake occurred and affected a sizable amount of the population, a rise in COVID-19 cases might be inevitable, despite all efforts, the team said in its recently published paper.
Studying the past
Ten years before COVID-19 spread around the world, a devastating magnitude-7.0 earthquake hit Port-au-Prince in Haiti. Eight months later, a cholera outbreak occurred. The damaged sanitation system and already overwhelmed healthcare system proved to be fertile ground for the epidemic to spread to 650,000 people and kill 9,000 people, on top of the 200,000 people who died from earthquake-related damages.
Natural disasters can force people from their homes and into relatively small, crowded shelters, allowing viruses to more easily spread. For instance, in 1991, the eruption of Mount Pinatubo, a volcano 54 miles (87 kilometers) from Manila in the Republic of the Philippines, preceded an outbreak of measles that caused over 18,000 cases among people who were forced to leave their homes.
More recently, in May 2020, a cyclone hit the west coast of India. The COVID-19 infection rate doubled in the following two weeks. Shelters were overwhelmed and may not have been particularly sanitary, Silva said.
Natural hazards of all types can exacerbate the effects of a pandemic. However, “geophysical hazards are a shock,” Silva said. You can typically forecast storms and estimate floods, but an earthquake is sudden and unexpected.
In addition to the Croatian earthquake, Silva and Paul studied other earthquakes that occurred during the pandemic, including in Khoy, Iran, on February 23, Elâzığ, Turkey, on January 23, 2020, and Salt Lake City, Utah on March 18.
The pair collected data on daily confirmed virus cases for those regions recently struck by earthquakes and determined if there was an impact on infection rate. Then, they simulated ground shaking from two earthquake scenarios in Portugal and calculated likely building damage. From these estimates, they determined how many people would be displaced in each of these earthquakes and therefore how many would be vulnerable to the virus.
The first scenario simulated a moderate magnitude-5.7 event onshore near the Metropolitan Area of Lisbon and the second looked at a strong magnitude-8.7 event offshore that could cause serious damage to Lisbon and other areas. For each earthquake scenario, the team also applied two possible cases: 1) an optimistic one in which there was some level of preparedness from emergency authorities, but the earthquake caused enough of a disruption to prevent the population from following all directives, and 2) a pessimistic case in which emergency authorities were not prepared and populations were not able to follow safety protocols.
The team found that following a magnitude-5.7 onshore earthquake, for the optimistic case there would be a 0.1 to 4.0% increase in COVID-19 cases in the Lisbon and Tagus Valley, which includes the metropolitan area of Lisbon. For the pessimistic case, there would be a 30 to 60% increase.
Following the simulated magnitude-8.7 offshore earthquake, there would be a 10-15% increase in COVID-19 cases in the Lisbon and Tagus Valley in the optimistic case. For the pessimistic case, there would be a greater than 60% increase.
The paper also identifies regions around the world that are at a higher risk for both a large seismic event and significant increase in COVID-19 cases, like California, Peru and Haiti. “We want to help decision makers as they formulate contingency and response plans to natural disasters like earthquakes during a pandemic,” Silva said.
Preparing for the future
We may not be able to see an earthquake coming in the same way we can see a storm brewing, but we can estimate rough probabilities of an earthquake occurring based on underlying geology and prior events. “Looking at the last 10 years in Italy, we had 46 earthquakes with a magnitude-4–4.9,” Mauro Dolce, the Scientific Advisor of the Chief of the Italian Civil Protection Department who was not directly involved with the study, said.
This means the probability of another earthquake of similar magnitude occurring in the next six months is 90%, according to Dolce. “And it’s likely that COVID-19 will last for six months or more.” The probability of an even larger magnitude-5–5.9 earthquake in the next six months is 26% based on prior events, Dolce said.
If a strong earthquake were to occur, people may relax COVID-19 social distancing protocols and forgo masks, among other protective gear, Dolce said. In his role with the Civil Protection Department, Dolce must understand all possible problems that could arise from a natural disaster. “We typically deal with one risk at a time,” Dolce said. Yet, the idea of dealing with multiple disasters at the same time has become increasing relevant in the past 5 to 10 years and has been brought to the forefront with COVID-19.
Silva and Paul’s study helps him understand different risks and prioritize official actions and regulations. “This is quite an original study,” Dolce said. “Having the idea – even a quantitative sense of what could happen during a catastrophic event – is important.”
“The study is interesting for policy and decision makers,” Dolce said. “It helps them better appreciate how the two risks interact and how important it is to be prepared to manage an event.”
Silva, V., & Paul, N. (2020). Potential impact of earthquakes during the 2020 COVID-19 pandemic. Earthquake Spectra, https://doi.org/10.1177/8755293020950328