Performance of personalized ventilation in mitigating short-range airborne transmission under the influence of multiple factors

The effectiveness of using personalized ventilation(PV)in mitigating airborne transmission risk was found to be easily affected by multiple factors.The aim of this study was hereby to evaluate the impacts of several important factors on the performance of PV in airborne disease control for closely ranged occupants.Orthogonal experiments were designed for CFD simulations under different levels of four selected factors.Results indicated that the order of significance of these four factors affecting the intake fraction(IF)of the exposed occupant was as follows:mode of PV use>relative distance between occupants>PV airflow volume>background ventilation.The best combination of the four tested factors was PV of 15 L/s for both the infected source and the exposed occupant,with a relative distance of 2 m between them and mixing ventilation,which would yield an IF of merely 0.0246%.The worst combination was PV of 6 L/s for the exposed occupant only,with a relative distance of 0.86 m under displacement ventilation,indicating an elevated IF of 0.2919%.The increase of PV air volume and relative separation distance both contributed to lower exposure risk,but they were not as influential as the mode of PV use.PV integrated with mixing ventilation and utilized for both infected and susceptible occupants were recommended.The findings in this study will be helpful to provide guidance for the implementation of PV in indoor environment for airborne infection control.

A relatively high zoonotic trematode prevalence in Orientogalba ollula and the developmental characteristics of isolated trematodes by experimental infection in the animal model

Background:Food-borne parasitic diseases decrease food safety and threaten public health.The snail species is an intermediate host for numerous human parasitic trematodes.Orientogalba ollula has been reported as intermediate hosts of many zoonotic trematodes.Here,we investigated the prevalence of zoonotic trematodes withinO.ollula in Guangxi,China,and assessed their zoonotic potential.Methods:Snails were collected from 54 sites in 9 cities throughout Guangxi.The snail and trematode larvae species were determined by combining morphological characteristics and molecular markers.The trematodes prevalence and constituent ratio were calculated and compared among different habitat environments.Phylogenetic trees of the trematode species were constructed using the neighbor-joining method with nuclear internal transcribed spacer 2(ITS2)sequences.The developmental cycles of the isolated trematodes were examined by experimental infection in ducks.The developmental characteristics ofEchinostoma revolutum was recorded by dissecting infected ducklings from 1-day post infection(dpi)to 10 dpi.Results:The overall prevalence of trematode larvae was 22.1%(1818/8238)inO.ollula from 11 sample sites.Morphological together with molecular identification,showed thatE.revolutum,Australapatemon sp.,Hypoderaeum conoideum,Pharyngostomum cordatum,andEchinostoma sp.parasitizedO.ollula,with the highest infection rate ofE.revolutum(13.0%).However,noFasciola larvae were detected.The trematodes prevalence and constituent ratio varied in two sub-biotypes(P<0.01).A neighbor-joining tree analysis of ITS2 sequences resulted in distinct monophyletic clades supported by sequences from isolated larvae with high bootstrap values.Ducklings exposed toO.ollula infected withEchinostoma sp.,E.revolutum,andH.conoideum larvae were successfully infected.The animal model forEchinostoma revolutum was successfully established.E.revolutum matured from larvae to adult at 10 dpi in the intestine of the duck,and the developmental characteristics ofE.revolutum were characterized by the maturation of the reproductive and digestive organs at 6-8 dpi.Conclusions:This study revealed a high prevalence of zoonotic trematodes inO.ollula from Guangxi,China.Existing trematodes infection in animals and human clinical cases,coupled with the wide geographical distribution ofO.ollula,necessitate further evaluations of the potential risk of spillover of zoonotic infection from animal to human and vice versa.