COVID-19 Roundup: Omicron Transmissibility, Obesity and Inflammation, and Long Symptoms

Transmissibility and Severity of Omicron¹

New research suggests that the omicron variant of SARS-CoV-2 may multiply 70 times faster than the delta variant, and therefore may be more transmissible.

The researchers compared lung tissue of individuals infected with the original SARS-CoV-2 virus, the delta variant, and the new omicron variant. At 24 hours after infection, the omicron variant had replicated faster than the original virus and the delta variant in the human bronchus. However, this variant of concern may result in less severe disease, as the omicron variant replicated approximately 10 times less than the original virus and the delta variant.

“It is important to note that the severity of disease in humans is not determined only by virus replication but also by the host immune response to the infection, which may lead to dysregulation of the innate immune system, ie, ‘cytokine storm,’” concluded study author Michael Chan, PhD. “It is also noted that, by infecting many more people, a very infectious virus may cause more severe disease and death even though the virus itself may be less pathogenic. Therefore, taken together with our recent studies showing that the omicron variant can partially escape immunity from vaccines and past infection, the overall threat from omicron variant is likely to be very significant.”

This research is currently undergoing the peer review process.

Obesity and Severe Disease²

SARS-CoV-2 infects human adipose tissue that results in an inflammatory response similar to that of severe COVID-19, according to the results of a recent study.

Mature adipocytes and adipose tissue macrophages were identified as the 2 cellular targets of SARS-CoV-2 infection. In autopsies of individuals with COVID-19, SARS-CoV-2 RNA was detected in adipocytes. SARS-CoV-2 RNA was also associated with an inflammatory infiltrate.

“Collectively, our data implies that infection in adipose tissue may partially explain the link between obesity and severe COVID-19,” the researchers concluded. “More efforts to understand the complexity and contributions of this tissue to COVID-19 pathogenesis are warranted.”

Long COVID-19 Symptoms³

Individuals with long COVID-19 symptoms had little improvement a year following infection, according to the preliminary results of a recent study.

Included in the study were 2230 adults who were hospitalized with COVID-19 in the United Kingdom. At 5 months after hospital discharge, 2.5 in 10 patients were fully recovered. Of the 807 participants assessed so far at 12 months following hospital discharge, less than 3 in 10 patients were fully recovered. Fatigue, muscle pain, slowing physically, poor sleep and breathlessness were among the most common long symptoms reported.

The data from 5 months following discharge indicate levels of severity of long symptoms. Symptoms were mild in 39% of participants, severe in 30% of participants, and very severe in 20% of participants. Additionally, 11% of patients reported moderate symptoms or primarily affected cognition.

Individuals with severe symptoms also had higher levels of substances associated with whole body inflammation, tissue damage and tissue repair. Individuals with poor cognition had higher levels of substances linked to brain fog.

—Leigh Precopio