Overall COVID risk for air travel is low, study says
Overall SARS-CoV-2 attack rates in airplane flights under 4 hours were less than 1%, according to a study of 177 flights departing from Wuhan, China, in January 2020. The results, published yesterday in Clinical Infectious Diseases, also indicated that people in the same row as an index case had the highest risk of infection.
Among 5,797 passengers, 175 were index patients and led to an upward estimate of 34 secondary cases. Estimates of attack rates had an upper bound of 0.60% and a lower bound of 0.3% (95% confidence intervals [CIs], 0.4% to 0.8% and 0.2% to 0.5%, respectively). Each index case infected 0.2 passengers in the upper-bound estimate and 0.1 passengers in the lower-bound estimate.
People sitting immediately next to the index patient had a much higher attack rate of 9.2% (95% CI, 5.7% to 14.4%), creating a relative risk of 27.8 (95% CI, 14.4 to 53.7) compared with other seats in the upper-bound estimation. Comparing overall window, middle, and aisle seats, the middle seat had the highest attack rate at 0.8%. Upper-bound attack rates went from 0.7% to 1.2% when the traveling time increased from 2.0 to 3.3 hours.
The study took place prior to COVID-19 mitigations, such as masks or physical distancing on planes, and the researchers did not have knowledge about relationships among travelers. However, they defined an index case as someone who was confirmed with COVID-19 post-travel, had symptom onset within 14 days before traveling or within 2 days after travel, and had the earliest date of symptom onset among passengers within 3 rows. Close contacts were passengers within 3 rows of the index case.
For upper-bound risks, the researchers assumed no relationship or contact between passengers before or after the journey, but for the lower-bound risk, passengers seated immediately next to the index patient were excluded if they had the same departure and destination.
Sep 21 Clin Infect Dis study
Dexamethasone may be less effective in LMICs, study says
Dexamethasone, which is used to treat critically ill COVID-19 patients, may be less effective in lower- and middle-income countries (LMICs) compared with high-income countries, according to a modeling study published yesterday in Clinical Infectious Diseases.
Accounting for healthcare capacities, epidemic trajectories, and drug efficacy without the help of supportive care, the researchers calculated that dexamethasone would prevent 22% of deaths in high-income countries and 8% of deaths in LMICs if COVID-19 epidemic mitigations were occurring. If the local epidemic was being poorly mitigated, then dexamethasone would prevent 18% of deaths in high-income countries and 5% in low-income countries.
Increasing the use of therapeutics that prevent COVID-19 or that stop illness from becoming severe could help the effectiveness of dexamethasone and other COVID-19 treatments, according to the researchers. If healthcare systems are stretched to capacity, however, fewer individuals who are hospitalized receive dexamethasone, and fewer hospitalized people receive supportive healthcare, which would maximize dexamethasone's effect.
"Our results show that effect sizes for therapeutics estimated in clinical trials will not necessarily provide a guide to their 'real-world' impact on COVID-19 disease burden as 'real-world' impact also crucially depends on prevailing healthcare constraints, the trajectory of the epidemic and the extent to which benefits persist in the absence of supportive care," the researchers conclude.
Sep 21 Clin Infect Dis study