In this week's roundup, the latest scientific research on the coronavirus and efforts to find treatments and vaccines suggest that infections by the omicron variant of the virus are contagious for at least six days, heart defects boost risks for hospitalized patients and the real death toll of the pandemic could be much higher than estimations.

Contagious for six days

Patients infected with the omicron variant of SARS-CoV-2 remain contagious for just as long as patients infected with earlier variants, according to a small study.

Researchers took blood samples from 56 newly-diagnosed patients, including 37 with delta infections and 19 with omicron infections. All were mildly ill, such as with flu-like symptoms, but none were hospitalized.

Regardless of which variant or whether or not they had been vaccinated or boosted, study participants "shed live virus for, on average, about six days after symptoms (began), and ... about one in four people shed live virus for over 8 days," said Dr. Amy Barczak of the Massachusetts General Hospital in Boston, who co-authored a report posted on medRxiv ahead of peer review.

"Although it is unknown exactly how much live virus is needed to spread the disease to others, we take these data to suggest that people with mild COVID-19 infection may be contagious on average for six days, and sometimes longer," Barczak said. "Decisions about isolation and masking should take such information into account, regardless of variant or prior vaccination status."

Heart defects boost risks

People born with heart defects who become sick enough from COVID-19 to be hospitalized are at higher risk for becoming critically ill or dying, researchers said.

The findings were drawn from a study that compared 421 patients with a heart defect who were hospitalized for COVID-19 with 235,638 similar hospitalized COVID-19 patients born with normal hearts.

After researchers accounted for patients' other risk factors, those with congenital heart defects were 40% more likely to be admitted to an intensive care unit, 80% more likely to need mechanical ventilation, and two times more to die while hospitalized, compared to patients in the control group, according to the report published on Monday in the journal Circulation.

Hospitalized patients with a congenital heart defect and another health condition faced even higher risks for poor outcomes, the researchers found.

"People with heart defects should be encouraged to receive the COVID-19 vaccines and boosters and to continue to practice additional preventive measures for COVID-19, such as mask-wearing and physical distancing," study leader Karrie Downing of the U.S. Centers for Disease Control and Prevention said in a statement.

Real death toll

The true death toll from the coronavirus pandemic may be more than three times higher than official records suggest, researchers said.

Instead of the official estimate of 5.9 million COVID-related deaths, a more realistic estimate is 18.2 million, according to a report in The Lancet on Thursday.

Researchers compared data from 74 countries and territories collected from January 2020 through December 2021 with data collected during the previous 11 years. On average, among every 100,000 people worldwide, there were 120 deaths that would not have been expected had the pandemic not occurred, they estimated.

The highest estimated excess death rates were in Andean Latin America (512 deaths per 100,000), Eastern Europe (345 deaths per 100,000), Central Europe (316 deaths per 100,000), Southern sub-Saharan Africa (309 deaths per 100,000), and Central Latin America (274 deaths per 100,000).

The United States and the United Kingdom had an estimated 179 and 127 excess deaths per 100,000, respectively. Some countries, including Iceland, Singapore and Australia, appeared to have had fewer deaths than expected.

The highest numbers of estimated pandemic-related deaths were in India (4.1 million), the U.S. and Russia (1.1 million each), Mexico (798,000), Brazil (792,000), Indonesia (736,000) and Pakistan (664,000).

"Further research will help to reveal how many deaths were caused directly by COVID-19, and how many occurred as an indirect result of the pandemic," study leader Haidong Wang of the University of Washington in Seattle said in a statement./Reuters