Epstein-Barr may play a role in some long COVID; coronavirus can impair blood sugar processing by organs - Reuters

People queue for COVID-19 testing in Macau, China, June 20, 2022. REUTERS/John Mak

June 27 (Reuters) - The following is a summary of some recent studies on COVID-19. They include research that warrants further study to corroborate the findings and that has yet to be certified by peer review.

Epstein-Barr virus may play role in some long COVID cases

COVID-19 may reactivate a common virus that lurks unseen in most people, and that effect might increase patients' risk of certain long-lasting symptoms, according to preliminary findings from a study. More than 90% of adults have been infected with Epstein-Barr virus (EBV). Most remained asymptomatic, but some developed mononucleosis as adolescents or young adults.

Among 280 patients with SARS-CoV-2 infections, including 208 with long COVID, researchers found that at four months after diagnosis, fatigue and problems with thinking and reasoning were more common in study participants with immune cells in their blood showing signs of recent EBV reactivation. These signs of reactivation were not linked with other long COVID findings such as gastrointestinal or heart and lung problems, however. And EBV itself was not found in patients' blood, which suggests any reactivation likely is transient and happens during acute COVID-19, Dr. Timothy Henrich of the University of California, San Francisco and colleagues reported on medRxiv ahead of peer review.

The findings do not prove that EBV reactivation caused patients' symptoms, Henrich said. And even if it did, "There are likely many other causes of long COVID symptoms such as persistent SARS-CoV-2 virus in tissues over time and a dysregulated immune system that may arise from viral persistence," he said. "Further study of various tissues is urgently needed, as are studies that follow participants from the time of acute infection to months or years thereafter."

SARS-CoV-2 can impair blood sugar processing by organs

Infection with the coronavirus impairs the activity of multiple genes involved in the body's chemical processes, including blood sugar metabolism, and for the first time researchers have seen these effects not just in patients' respiratory tract but elsewhere in the body.

Japanese researchers analyzed blood and tissue samples from patients with mild or severe COVID-19 and from healthy volunteers, evaluating the "expression" - or activity levels - of genes that control the so-called insulin/IGF signaling pathway, which in turn affects many body functions necessary for metabolism, growth, and fertility. "The results were striking," study leader Iichiro Shimomura of Osaka University said in a statement. "Infection with SARS-CoV-2 affected the expression of insulin/IGF signaling pathway components in the lung, liver, adipose tissue, and pancreatic cells." The resulting disruptions in blood sugar metabolism likely contribute to COVID-19's effects on organs, the researchers said.

The changes, which they attribute in part to the immune system's inflammatory response to the virus, were more pronounced in patients with severe COVID-19, they reported in the journal Metabolism. In test tube experiments, dexamethasone - which is known to benefit hospitalized patients with COVID-19 - helped relieve the adverse effects of the virus on the genes.

The new findings might be a clue to why some patients develop metabolic complications during or after COVID-19, such as insulin resistance, hyperglycemia, hyperlipidemia, and new onset of diabetes, the researchers said.

New data support 5 days of isolation plus 5 days of masking

A new study supports current guidelines that call for a five-day isolation period for COVID-19 infections followed by five days of strict masking to help prevent transmission from cases that remain culture positive, researchers said.

Boston University School of Medicine researchers collected daily nasal swabs for at least 10 days from 92 vaccinated college students and staff infected with the Delta or Omicron variants of the coronavirus for analysis with PCR and with the kind of rapid-antigen tests that are available for home use. Among these young and otherwise healthy adults, only 17% still tested positive after five days, and no one was infectious beyond 12 days after symptom onset, the researchers reported in Clinical Infectious Diseases. The results were similar regardless of variant or vaccine booster status, and negative rapid antigen tests were very reliable, according to the report.

While rapid antigen testing "may provide reassurance of lack of infectiousness... a full 10 days is necessary to prevent transmission from the 17 percent of individuals who remain culture positive after isolation," study leader Dr. Tara Bouton said in a statement.

Click for a Reuters graphic on vaccines in development.

Reporting by Nancy Lapid; Editing by Bill Berkrot

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