An association between exposure to Middle East Respiratory Syndrome (MERS) and mortality rate of Coronavirus Disease 2019 (COVID-19).

OBJECTIVE: Our objective was to find an association between exposure of a population to Middle East Respiratory Syndrome Coronavirus (MERS-CoV) and mortality rate due to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) across different countries worldwide. MATERIALS AND METHODS: To find the relationship between exposure to MERS-CoV and mortality rate due to SARS-CoV-2, we collected and analyzed data of three possible factors that may have resulted in an exposure of a population to MERS-CoV: (1) the number of Middle East Respiratory Syndrome (MERS) cases reported among 16 countries since 2012; (2) data of MERS-CoV seroprevalence in camels across 23 countries, as working with camels increase risk of exposure to MERS-CoV; (3) data of travel history of people from 51 countries to Saudi Arabia was collected on the assumption that travel to a country where MERS is endemic, such as, Saudi Arabia, could also lead to exposure to MERS-CoV. RESULTS: We found a significantly lower number of Coronavirus disease 2019 (COVID-19) deaths per million (deaths/M) of a population in countries that are likely to be exposed to MERS-CoV than otherwise (t-stat=3.686, p<0.01). In addition, the number of COVID-19 deaths/M of a population was significantly lower in countries that reported a higher seroprevalence of MERS-CoV in camels than otherwise (t-stat=4.5077, p<0.01). Regression analysis showed that increased travelling history to Saudi Arabia is likely to be associated with a lower mortality rate due to COVID-19. CONCLUSIONS: This study provides empirical evidence that a population that was at an increased risk of exposure to MERS-CoV had a significantly lower mortality rate due to SARS-CoV-2, which might be due to cross-protective immunity against SARS-CoV-2 in that population because of an earlier exposure to MERS-CoV.