The following is a roundup of some of the latest scientific studies on the novel coronavirus and efforts to find treatments and vaccines for COVID-19, the illness caused by the virus.

Genetic profiles may predict COVID-19 risk

Large-scale genetic screening to identify populations vulnerable to COVID-19 may well be possible, according to researchers in France. In laying out their hypothesis in the journal Trends in Genetics, they described two opposing enzyme processes that occur when the coronavirus enters the body.

One process contributes to infection by helping the virus break into cells. The other — an opposite process — protects the body by keeping the virus away from its target cells.

Among individuals, they said, genetic differences affect the strength of these infection and protection mechanisms, with some people having genes that predispose them to infection and others having genes that strengthen the body's protective process.

If a genetic risk score were developed based on the information in the genetic databases the researchers analyzed, then populations at risk for severe COVID-19 "could be characterized by specific genetic profiles," study co-author Gerard Milano of Antoine Lacassagne Cancer Center in Nice told Reuters. (https://bit.ly/3fYZA7W)

Nursing homes may be safer when workers live-in

Compared to nursing homes in France where staff members came and went during the coronavirus pandemic, facilities where workers chose to confine themselves with residents had a lower rate of coronavirus infections among residents and staff and fewer COVID-19 deaths among residents, research showed.

In many countries, nursing homes have experienced large numbers of COVID-19 deaths, with the elderly often particularly vulnerable to the illness. Researchers compared 17 nursing homes where staff stayed with residents and 9,513 nursing homes where staff members left when shifts ended.

Coronavirus infections developed in one self-confining facility (6%) and in 4,599 of the other facilities (48%), they reported on Thursday in the journal JAMA Network Open.

In facilities where the staff self-confined, the COVID-19 rate among residents was 0.4%, compared to nearly 4% at the other homes. Residents at facilities where staff members self-confined also were nearly 80% less likely to die of COVID-19.

Furthermore, rates of possible or confirmed COVID-19 were 2% among staff members who self-confined, compared with 8% among those who went home every day.

The findings "suggest that self-confinement of staff members with residents may help protect nursing home residents," the researchers said. "The staff members did something out of the ordinary by confining themselves with the residents" and "putting aside their personal lives by staying in the facility for several weeks, night and day," study co-author Dr. Joel Belmin of Pitie-Salpetriere-Charles Foix Hospital in Paris told Reuters. (https://bit.ly/2Y3NlRo)

Virus transmission risk high within households

The greatest risk of coronavirus transmission is among people who live together, a study from China indicated.

Early this year, researchers in China traced 3,410 close contacts of 391 COVID-19 patients to determine the rate at which infected individuals transmitted the virus. The so-called secondary attack rate was 0.1% on public transportation and 1.0% in healthcare settings — where mask wearing was mandatory — but it was 10.3% in households. Secondary attack rates increased as patients' symptoms became more severe.

Overall, patients' risk of infecting others increased nearly five-fold if they were coughing up phlegm or mucus. Secondary attack rates in other countries might be different because China implemented strict quarantines and other measures to control the coronavirus outbreak.

"However," the researchers wrote on Thursday in the journal Annals of Internal Medicine, "the risk for secondary infection via household contact was still highest compared with other contact settings because people spent more time at home, which led to more frequent and longer unprotected exposure." (https://bit.ly/2Y38ICt)

No effects on placenta seen with late-pregnancy COVID-19

Coronavirus infection late in pregnancy does not appear to affect the microscopic structure of the placenta, which is the key organ for pregnancy and fetal growth.

Researchers examined third-trimester placentas from 21 women with COVID-19 and 20 women who had negative coronavirus test results. Compared to placentas from women who tested negative for the virus, placentas from infected women showed no differences in cells or tissue structure, or in blood flow issues, the authors reported in a paper posted on the website medRxiv on Wednesday ahead of peer review.

There were also no significant differences in placental weight or in the relationship between placental and fetal weight, two indicators of how well the placenta is functioning.

While coronavirus infections that occur earlier in pregnancy might have greater impacts on the placenta, "our study suggests that COVID-19 infection during late pregnancy (third trimester) might not produce demonstrable pathology," study co-author Dr. Mai He of Washington University in St. Louis School of Medicine told Reuters. (https://bit.ly/3gXi4an)