Introduction
Brucellosis is one of the most common zoonotic diseases globally (Dean, Schelling, & Zinsstag, 2014). More than 500,000 new human cases of brucellosis are reported annually (Deng, Liu, Duan, & Peng, 2019), and millions of livestock are either infected or at risk (Pappas, 2010). It is a significant public health problem and causes serious harm to the development of the livestock industry and human health (Saddique et al., 2019). Brucella is most commonly transmitted by indirect or direct contact with infected livestock and the consumption of contaminated raw milk or their products (Kairu-Wanyoike et al., 2019). At present, 12 species have been identified in Genus Brucella , including six classical species and six newly detected biovars. Among them, Brucella melitensis is the most severe both in infectiousness and pathogenicity to humans (Eschenbrenner et al., 2002). Fever, fatigue, sweating, and muscle and joint pain are the main manifestations in the acute stage of human brucellosis (W. Jiang et al., 2019). The pathogen can invade various systems of the human body and seriously affect the quality of life (Venyo, 2015).
Brucella spp. are highly infectious because the infectious dose by an aerosol is only 10 to 100 organisms (D. L. Sewell, 2006), and it has been considered the most important laboratory-acquired bacterial infection (Al Dahouk & Nöckler, 2011). Aerosol transmission generated accidentally or during microbiologic techniques from contaminated materials are the proposed routes of transmission (Bossi et al., 2004; Lowe et al., 2015). As aerosolization is the primary mechanism of transmission in this setting (Memish & Mah, 2001), it is recommended that the organism be handled according to level 3 biosafety precautions (Fiori, Mastrandrea, Rappelli, & Cappuccinelli, 2000). These guidelines can be challenging to follow, particularly in regions with a low incidence of brucellosis. All the Brucella spp. have been implicated in laboratory-associated infections, and they may account for up to 2% of all laboratory-associated infections (Robichaud, Libman, Behr, & Rubin, 2004). In China, several cases of brucellosis are reported annually, but no national surveillance system specifically identifies laboratory-acquired cases. Therefore, the epidemiological profile of brucellosis resulting from laboratory transmission and S2 vaccine outbreak events of brucellosis in China remains unknown. The purpose of this study is to summarize laboratory-acquired infection and S2 vaccine outbreak events of brucellosis in China so that effective countermeasures for the prevention of laboratory-acquired infections and the promotion of public health safety can be designed.