Physical, cognitive, and social triggers of symptom fluctuations in people living with long COVID: an intensive longitudinal cohort study

Background. Symptom fluctuations within and between individuals with long COVID are widely reported, but the extent to which severity varies following different types of activity and levels of exertion, and the timing of symptoms and recovery, have not previously been quantified. We aimed to characterise timing, severity, and nature of symptom fluctuations in response to effortful physical, social and cognitive activities, using Ecological Momentary Assessments. Methods. We recorded activity, effort, and severity of 8 core symptoms every 3 h for up to 24 days, in cohorts from both clinic and community settings. Symptom severities were jointly modelled using autoregressive and moving average processes. Findings. Consent was received from 376 participants providing ≥1 week's measurements (273 clinic-based, 103 community-based). Severity of all symptoms was elevated 30 min after all categories of activity. Increased effort was associated with increased symptom severity. Fatigue severity scores increased by 1.8/10 (95% CI: 1.6–1.9) following the highest physical exertions and by 1.5 (1.4–1.7) following cognitive efforts. There was evidence of only mild delayed fatigue 3 h (0.3, 0.2–0.5) or one day later (0.2, 0.0– 0.5). Fatigue severity increased as the day progressed (1.4, 1.0–1.7), and cognitive dysfunction was 0.2 lower at weekends (0.1–0.3). Interpretation. Cognitive, social, self-care and physical activities all triggered increased severity across every symptom, consistent with associated common pathways as potential therapeutic targets. Clear patterns of symptom fluctuations emerged that support more targeted self-management. Funding. National Institute for Health and Care Research

Regulation of the Mycobacterium tuberculosis hypoxic response gene encoding α-crystallin

Unlike many pathogens that are overtly toxic to their hosts, the primary virulence determinant of Mycobacterium tuberculosis appears to be its ability to persist for years or decades within humans in a clinically latent state. Since early in the 20th century latency has been linked to hypoxic conditions within the host, but the response of M. tuberculosis to a hypoxic signal remains poorly characterized. The M. tuberculosis α-crystallin (acr) gene is powerfully and rapidly induced at reduced oxygen tensions, providing us with a means to identify regulators of the hypoxic response. Using a whole genome microarray, we identified >100 genes whose expression is rapidly altered by defined hypoxic conditions. Numerous genes involved in biosynthesis and aerobic metabolism are repressed, whereas a high proportion of the induced genes have no known function. Among the induced genes is an apparent operon that includes the putative two-component response regulator pair Rv3133c/Rv3132c. When we interrupted expression of this operon by targeted disruption of the upstream gene Rv3134c, the hypoxic regulation of acr was eliminated. These results suggest a possible role for Rv3132c/3133c/3134c in mycobacterial latency