Could the ambient higher temperature decrease the transmissibility of COVID-19 in China?

BACKGROUND: Existing literatures demonstrated that meteorological factors could be of importance in affecting the spread patterns of the respiratory infectious diseases. However, how ambient temperature may influence the transmissibility of COVID-19 remains unclear. OBJECTIVES: We explore the association between ambient temperature and transmissibility of COVID-19 in different regions across China. METHODS: The surveillance data on COVID-19 and meteorological factors were collected from 28 provincial level regions in China, and estimated the instantaneous reproductive number (Rt). The generalized additive model was used to assess the relationship between mean temperature and Rt. RESULTS: There were 12,745 COVID-19 cases collected in the study areas. We report the associated effect of temperature on Rt is likely to be negative but not of statistical significance, which holds for most Chinese regions. CONCLUSIONS: We found little statistical evidence for that the higher temperature may reduce the transmissibility of COVID-19. Since intensive control measures against the COVID-19 epidemics were implemented in China, we acknowledge this may impact the underlying effect size estimation, and thus cautiousness should be taken when interpreting our findings.

Lung injury induced by short-term mechanical ventilation with hyperoxia and its mitigation by deferoxamine in rats.

BACKGROUND: Long-term mechanical ventilation with hyperoxia can induce lung injury. General anesthesia is associated with a very high incidence of hyperoxaemia, despite it usually lasts for a relatively short period of time. It remains unclear whether short-term mechanical ventilation with hyperoxia has an adverse impact on or cause injury to the lungs. The present study aimed to assess whether short-term mechanical ventilation with hyperoxia may cause lung injury in rats and whether deferoxamine (DFO), a ferrous ion chelator, could mitigate such injury to the lungs and explore the possible mechanism. METHODS: Twenty-four SD rats were randomly divided into 3 groups (n = 8/group): mechanical ventilated with normoxia group (MV group, FiO2 = 21%), with hyperoxia group (HMV group, FiO2 = 90%), or with hyperoxia + DFO group (HMV + DFO group, FiO2 = 90%). Mechanical ventilation under different oxygen concentrations was given for 4 h, and ECG was monitored. The HMV + DFO group received continuous intravenous infusion of DFO at 50 mg•kg- 1•h- 1, while the MV and HMV groups received an equal volume of normal saline. Carotid artery cannulation was carried out to monitor the blood gas parameters under mechanical ventilation for 2 and 4 h, respectively, and the PaO2/FiO2 ratio was calculated. After 4 h ventilation, the right anterior lobe of the lung and bronchoalveolar lavage fluid from the right lung was sampled for pathological and biochemical assays. RESULTS: PaO2 in the HMV and HMV + DFO groups were significantly higher, but the PaO2/FiO2 ratio were significantly lower than those of the MV group (all p < 0.01), while PaO2 and PaO2/FiO2 ratio between HMV + DFO and HMV groups did not differ significantly. The lung pathological scores and the wet-to-dry weight ratio (W/D) in the HMV and HMV + DFO groups were significantly higher than those of the MV group, but the lung pathological score and the W/D ratio were reduced by DFO (p < 0.05, HMV + DFO vs. HMV). Biochemically, HMV resulted in significant reductions in Surfactant protein C (SP-C), Surfactant protein D (SP-D), and Glutathion reductase (GR) levels and elevation of xanthine oxidase (XOD) in both the Bronchoalveolar lavage fluid and the lung tissue homogenate, and all these changes were prevented or significantly reverted by DFO. CONCLUSIONS: Mechanical ventilation with hyperoxia for 4 h induced oxidative injury of the lungs, accompanied by a dramatic reduction in the concentrations of SP-C and SP-D. DFO could mitigate such injury by lowering XOD activity and elevating GR activity.