Risk assessment of Lassa fever importation into China, 2021–2025

  Objective  Lassa fever is endemic in West Africa, causing about 5 000 deaths every year. With the increasing trade and travel between China and Africa, the probability of importation of Lassa fever from Africa to China is on the rise. This study aims to access the risk of importation of Lassa fever into China in the next five years.

  Methods  Based on the previous risk assessment methods of Ebola virus disease and Zika virus disease, the probability of importation of Lassa fever from African to China, its further transmission and its consequences are qualitatively and quantitatively estimated according to its mode of transmission, epidemic status, personnel and goods exchanges between China and Africa, and the facts of importation and further transmission from other countries, and then a comprehensively evaluation of the risk of the transmission into China was made.

  Results  In the context of the global pandemic of coronavirus disease 2019 (COVID-19), China has restricted the entering of international travelers and taken strict measures to prevent and control the importation of COVID-19. It is estimated that China will face a very low risk of Lassa fever in 2021. With the resumption of travel between China and Africa, the number of apparent infection cases of Lassa fever from Africa to China might be 0–1 case/year by 2025. The mortality of imported apparent infection case might be high (about 35%) due to late detection and treatment. In the past, the probability of secondary transmission caused by imported Lassa fever case was low (about 0.40%–5.09%), and there has been no reports of third generation transmission or epidemic in the animals in the former non-Lassa fever endemic area. For the 51 years since the first detection, Lassa fever is still endemic in West Africa.

  Conclusion  The probability of importation of Lassa fever to China from Arica would be very high in the next 5 years. The probabilities of its secondary transmission would be low and third generation transmission would be very low in China. Lassa fever will cause no local transmission after the importation into China under current conditions.