What is known about this topic? Few major outbreaks of coronavirus disease 2019 have occurred in China after major nonpharmaceutical interventions and vaccines have been deployed and implemented. However, sporadic outbreaks that had high possibility to be linked to cold chain products were reported in several cities of China.. What is added by this report?In July 2020, a COVID-19 outbreak occurred in Dalian, China. The investigations of this outbreak strongly suggested that the infection source was from COVID-19 virus-contaminated packaging of frozen seafood during inbound unloading personnel contact. What are the implications for public health practice? Virus contaminated paper surfaces could maintain infectivity for at least 17-24 days at -25 ℃. Exposure to COVID-19 virus-contaminated surfaces is a potential route for introducing the virus to a susceptible population. Countries with no domestic transmission of COVID-19 should consider introducing prevention strategies for both inbound travellers and imported goods. Several measures to prevent the introduction of the virus via cold-chain goods can be implemented. INVESTIGATION AND RESULTSCOVID-19 cases were diagnosed by a local hospital in Dalian according to the Protocol for Prevention and Control of COVID-19 (Edition 6) issued by China CDC (1). In this study, a confirmed case was defined as having a throat swab that tested positive for COVID-19 virus RNA by RT-qPCR; an undiscovered infected case was defined as having a sera sample that tested positive for COVID-19 antibodies but negative for COVID-19 virus RNA. Detailed epidemiological investigation for early cases were conducted through in-person interviews for their travel history, activity, work history, and contact history starting 14 days (incubation period) before the onset of illness. Environmental samples and cold-chain product samples collected from Company K were further tested with RT-qPCR. Individuals who had contact with the China CDC Weekly Chinese Center for Disease Control and Prevention CCDC Weekly / Vol. 3 / No.

A thermal imager was used for measuring the canopy temperature to calculate crop water stress index (CWSI) of rice under water deficit condition. The CWSI varied diurnally with peaks appeared at noon, and soil water deficit led to higher CWSI values during noon. Transpiration rate (Tr), stomatal conductance (gs) and net photosynthetic rate (Pn) were high at low CWSI, and reduced with increasing CWSI. The relationship between CWSI and Pn, Tr or gs at noon was described by quadratic polynomial equations. At critical noon, CWSI values for the decline trend in Pn (0.303, 0.385 and 0.446 at tillering, panicle initiation to booting, milk to soft dough stage) were higher than for decline in Tr and gs. Assuming a 5% reduction in Pn from maximum is moderate water deficit, the critical CWSI values were 0.420, 0.472 and 0.536 at tillering, panicle initiation to booting and milk to soft dough stages. CWSI at 14:00 decreased significantly with increasing relative soil moisture contents. There was a slight difference between the linear relations under different vapor pressure deficit (VPD) conditions. The critical relative soil moisture contents for a 5% reduction in Pn were 1.57%, 1.18% and 1.27% higher under high VPD than low VPD conditions. It implied that rice water status was determined in conjunction with field soil moisture content and air aridity. The water deficit diagnosis based on canopy temperature tracked by thermal infrared imager is a promising method in reflecting the conjuncted function of soil moisture deficit and air aridity on crop water status.

Although the main function of rice fields is to produce rice, they also provide a range of other ecosystem services [1], including O 2 production, CO 2 reduction, summer temperature cooling, flood mitigation, and so on [2]. Meanwhile, paddy fields have a negative effect on the environment through greenhouse gas emissions and agricultural non-point pollution [3-4]. Much literature has evaluated these ecosystem services by rice paddies, and these results show that rice fields provide more positive values in maintaining the sustainability of a regional or even global ecosystem [5-7]. Ecosystem services have been recognized throughout the rice-growing world and been considered in agricultural policy-making [8-9].