Genetic Profiles May Predict COVID-19 Risk; Household Transmission High

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.

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."

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.

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—Nancy Lapid