Assessing the risk of MERS importation from South Korea into cities of China: a retrospective study

Abstract

On May 20th, 2015, the Republic of Korea reported its first laboratory-confirmed case of Middle East respiratory syndrome coronavirus(MERS-CoV) infection, followed by the largest outbreak of MERS-CoV outside of the Middle East, which included a case imported from South Korea into China. To understand the risk of MERS importation into China, we analyzed the epidemic situation of MERS globally, especially in South Korea, using the data of MERS cases notified to the World Health Organization. Then the volumes and travel destinations of passengers from South Korea to China were explored based on the historic flight itinerary data in June 2014. The relative probability of MERS importation from South Korea to cities in China was retrospectively assessed with the assumptions:(i) the same probability of MERS-CoV infection in the population of South Korea;(ii) an equal chance of traveling from South Korea to the cities in China between the infected and uninfected population;(iii) the same mobility pattern of air travelers in 2014 and 2015;(iv) the epidemic of MERS was stable during the study period in 2015;(v) the volume of air traveler from South Koreas has a potential correlation with the importation risk of MERS-CoV from the Republic of Korea to China. As of September 2nd, 2015, 26 countries have reported 1542 laboratory-confirmed MERS cases, including 185 cases in the Republic of Korea. In June 2014, a total of 1978647 passengers departed from the Republic of Korea by airplane, of which 697922(35.3%) travelers arrived in the mainland of China, Hong Kong and Macao Special Administrative Region of China. The primary airports of entry into China were located in Shanghai, Hong Kong, Beijing, and Qingdao. With the assumptions of this study, if a passenger with MERS-CoV infection traveled from South Korea to China, there was a highest probability(23.2%) of entry into the cities in Pearl River Delta(Hong Kong, Guangzhou, Shenzhen and Macao) with a secondary probability to cities in Yangtze River Delta(21.6%), Beijing and Tianjin(15.5%), and cities in Shangdong province(12.2%). Among the four primary destinations(Hong Kong, Shanghai, Beijing and Qingdao) of the travelers from South Korea, the entry airport will be most likely located in Hong Kong(34.9%) for the case departing from Seoul, and Shanghai(30.4%) and Beijing(29.5%) for the infected passenger departing from Busan, and Shanghai(67.0%) if the case leaved from Jeju Island of South Korea. In reality, we found that Hong Kong was the entry point of the imported MERS case from Seoul of South Korea, then travelling to the mainland of China via ground transportations. This study shows that there was a variable risk of MERS importation from South Korea into Chinese cities via commercial air travel, which can provide relative basis for assessing the high risk areas of the importation of MERS and the development of the pre-warming system and the control methods. China could heighten surveillance at the primary points of entry and leading destination cities of China, as a means to detect individuals with MERS-Co V infection at the earliest possible stage.

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ORCID for Shengjie Lai: orcid.org/0000-0001-9781-8148

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