As society adapts to controlling this highly infectious foe and as our understanding of this virus increases—what do we currently know of household secondary transmission? In a definitive systemic review by Dr Shah and colleagues from the Indian Institute of Public Health, they address this important question.
They highlight more recent studies which show, that with self-isolation of the index case within families there is a <20% risk of transmission to another household member. The risk is enhanced if the index case is symptomatic and partners of the index case and the elderly with comorbidities are particularly at risk. Factors outside the home—for example, regional prevalence and lockdown status, do not influence the transmission rate within the home.
The secondary attack rates reported within households associated with a stable external R0 suggest transmission is both driven by a relatively small number of high-risk contacts and low level of external transmission to other households in the area. In addition, the fact that 50–95% of contacts did not develop infection, despite regular contact with the index household case, suggests a degree of natural immunity to the virus.
Inhaled hydrogen and its anti-inflammatory properties in chronic inflammatory respiratory diseases
A key strategic role of the QJM is to highlight potential novel therapeutic pathways for human diseases. In the context of novel anti-inflammatory pathways specifically targeting the lung, the journal has recently published novel observations on this subject.1–4 We continue this tradition with the publication by Dr Wand and colleagues from Peking Union Medical College in which they describe the anti-inflammatory effects of inhaled hydrogen in patients with chronic respiratory diseases, specifically asthma and chronic obstructive pulmonary disease (COPD).
Hydrogen has been known to possess potent anti-oxidant properties and in vivo animal models of asthma has shown it to have the capacity to alleviate airway hyper-responsiveness. The authors report their observed anti-inflammatory effect of inhaled hydrogen in asthmatic and COPD patients. They used low inhaled concentrations of hydrogen (2.4%) and analyzed pro-inflammatory cytokine levels in exhaled breath condensate before and after 45 min of inhaled hydrogen with a significant observed post-treatment effect. In the current pandemic, one wonders would a similar anti-inflammatory effect be observed in COVID-19 patients?
Conflict of interest. None declared.
References
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