Silent War to Emerging or Re-emerging Respiratory Infection Diseases Badly Kept in Mind

Zheng, Ya-Li; Gao, Zhan-Cheng

The primary pattern that MERS spread among human being is close person-to-person contacts via droplets from patients, contaminated surfaces or equipment, and aerosol generated during aerosol-generating procedures. Nosocomial and home-based transmission have both occurred and have been proved by genome deep sequencing data in the past 3 years. [9, 11] MERS-CoV infection associated with considerable mortality (35.6%, as of June 26, according to data of WHO), [12] especially in individuals with underlying comorbidities, such as diabetes, renal failure, chronic lung disease, and immunocompromised status. [13] Fortunately, it does not seem to have the ability of sustainable human-to-human transmission. The basic reproduction number of MERS-CoV, Ro is <1 in early studies, [11, [14] [15] [16] which indicated the self-limited transmission and persistence of the disease requires continued animal-to-human infections. [17] But the possibility of epidemic also had been warned because of the limited data, the potential impact of stringent control measures which had already been taken, and the assumption authors made that asymptomatic patients do not transmit infection. [14] The ongoing outbreak in South Korea might confirm their fear. As of June 30, 2015, the Health Ministry of South Korea revealed 182 confirmed MERS cases, including 33 deaths (18.1%), 15 health care professionals (8.2%) infected, and 2638 contacts still in quarantine. [18] Cases called "super-spreaders" (such as patient no. 1 and patient no. 14, which infected 36 and 70 patients, respectively) emerged without finding any remarkable mutations in MERS-CoV strains that could contribute to easy transmissibility. [19] This outbreak is too fast and unexpected to be explained just by the suboptimal infection prevention practices and delayed diagnostic process, or regional habit variations like "doctor shopping" or "family nursing." The possibility of airborne transmission through suboptimal central air conditioning system in hospital settings should be seriously taken into account as well. MERS-CoV might be able to survive in the central air conditioning system, and spread through the vent pipe to the whole health care facilities, just like the situation once occurred in 2003, when SARS cases increased dramatically attributing to the rapid spread of the virus through drainage systems, in Taoda Garden, Hong Kong Special Administrative Region, China. [20] More details should be valued and investigated carefully for better understanding of MERS-CoV transmission patterns.