According to a study by US health authorities published on Friday, people contracting Covid-19 infect around half of their family members who live with them.

Adults appear to be more contagious than children, according to the study based on 101 cases of Covid-19 observed in two cities in the United States.

People who contract Covid-19 infect about half of their family members who live with them, and adults appear to be more contagious than children, according to a study by U.S. health officials released on Friday.

Many studies in the mode have attempted to determine the exact risk of transmission within a family, with widely varying results, but suggesting that children are less likely to be vectors of the coronavirus than adults.

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A secondary infection rate of 53%

The new study from the Centers for Disease Prevention and Control (CDC) is based on 101 cases of Covid-19 in two cities, Nashville (Tennessee) and Marshfield (Wisconsin), as of last April.

The researchers followed 191 household members of these 101 "index" cases, asking them to keep a diary of their possible symptoms, and to collect samples (nasal and / or saliva) for 14 days.

102 of these 191 contact cases ended up with a positive diagnostic test, for a secondary infection rate of 53%.

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Less than half of infected household members had symptoms when they tested positive

Among the initial 20 cases under 18, the secondary infection rate was 43%, while it was 57% for the 82 adults.

The few index children (20), however, make it difficult to generalize the result.

The authors also conclude: "Significant transmissions have occurred, whether the index patient was an adult or a child."

Another lesson is that less than half of infected household members had symptoms when they tested positive, underscoring the risk of asymptomatic transmission.

The CDC recommends that people who think they have been infected isolate themselves at home, sleep in a separate room, use a separate bathroom if possible, and wear a mask.