New Albany Med Research Sheds Light on Infectiousness of Covid-19

ALBANY — Researchers at Albany Medical College and Albany Medical Center Hospital found that patients with SARS-CoV-2, the virus that causes Covid-19, are infectious only during the initial onset of symptoms.

The study, published in the August 2021 issue of the Journal of Clinical Virology, and released Aug. 31, was a collaborative effort between Albany Med’s Departments of Immunology and Microbial Disease, Pathology and Laboratory Medicine, Emergency Medicine, and Epidemiology.

“This illuminating study has implications within the hospital, as we work to effectively isolate infectious patients, and for the larger community, in terms of knowing when we can safely discharge patients who no longer need the high level of care offered in the hospital,” said Dennis P. McKenna, M.D., president and CEO of Albany Med, in a statement.

A nucleic acid amplification test (NAAT) from nasopharyngeal and throat swabs is the gold standard for diagnosing Covid-19. However, this test doesn’t distinguish between active virus and other viral genomic fragments that no longer contain active virus, said Dennis W. Metzger, Ph.D., professor and chair of the Department of Immunology and Microbial Disease at Albany Medical College and one of the lead authors of the study.

Beginning in the early days of the pandemic in 2020, instead of relying solely on the NAATs, also known as the PCR test, Albany Med researchers used complex virus culture methods combined with assays to analyze antibodies in samples from congregate care Covid-19 patients hospitalized at Albany Medical Center Hospital.

As expected, they found that the patients expressed infectious virus very early after being admitted to the hospital. However, subsequent samples from the same patients showed that the patients quickly developed mucosal antibodies that suppress viral replication – that is, the virus was no longer reproducing itself. This was the case even when the patients continued to test positive for Covid-19 by PCR, sometimes weeks after the initial infection.

Dr. Metzger explained that active virus was likely present in the early stages of infection because antibody levels were low. “But as the disease progresses and the body produces larger amounts of antibody, the virus is effectively neutralized and the patient becomes noninfectious,” he said.

The study was done using patients with the original Covid-19 virus, not the Delta variant, but researchers say the results would be applicable to the Delta variant and other variants as well.

In Saratoga County, the 7-day rolling positivity infection rate was 4.6%, as of Aug. 31. According to Saratoga County Public Health Services, 67.8% of county residents have completed the vaccine series.