The mystery of the silent sick

The mystery of the silent sick

© Andrew Kelly / Reuters
People sit in painted circles in Domino Park in New York.

Several studies suggest that a large number of corona infected people remain symptom-free. What effects this could have on the course of the pandemic.

The mystery of the silent sick

In mid-March 2020, the Greg Mortimer at sea. 217 passengers and crew members embarked on a journey through the Antarctic in the footsteps of British explorer Ernest Shackleton. All of the people on board had a normal body temperature at this point, and nobody showed symptoms that are typical of Covid-19. Everyone was fine for seven days, but on the eighth day the first passenger got a fever. The guests were no longer allowed to leave their cabins, the crew provided them with food – in full protective gear. However, the measures could not prevent the majority of the people on the ship from becoming infected. According to tests, at least 60 percent of travelers had contracted Sars-CoV-2 in the end.

The events on the Greg Mortimer have now reconstructed Australian scientists in detail. Amazing at the in the specialist journal thorax The most recent investigation is that a large number of those infected showed no signs of the disease. Only 20 percent of them, or 24 people, had symptoms. Half of the sufferers suffered from breathing problems and had to be taken to a hospital by ship; one passenger died. The remaining 80 percent of ship travelers remained symptom-free.

According to a Chinese study, women in particular did not get sick despite infection

How many infections are asymptomatic is one of the major unanswered questions in the Covid 19 pandemic. Studies have led to very different results. So was the proportion of asymptomatic virus carriers on board the cruise ship Diamond Princess estimated at 18 percent. In contrast, studies from Italy showed values ​​of up to 75 percent.

It is also difficult to assess the effects of a high number of asymptomatic carriers. On the one hand, it could mean that far more people may have been infected than are officially recorded. Because people who feel healthy are less likely to be tested. This would give the population greater immunity than previously estimated, at least for a certain time. On the other hand, asymptomatic – and thus often undetected – infected people make the containment of the pandemic much more complicated. The outbreak was most likely on the Greg Mortimer triggered by infected people who had no or no symptoms at all, says Australian epidemiologist Heath Kelly: “This again shows how difficult it is to control Covid-19.” To what extent symptom-free infected people pass on the virus is also still unclear.

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A study that is currently published in the journal also provides new insights into those who remain symptom-free Jama Network Open has appeared. Researchers from China had examined 78 people who tested positive for Sars-CoV-2. It was not a random sample. All infected had had contact with the sick or visited the fish market in Wuhan, which is considered a possible source of the pandemic. 42 percent of these people were spared the Covid symptoms. They differed from the sick especially in gender and age. On average, they were only 37 years old, while their sick countrymen had an average age of 56 years, and two thirds of those without symptoms were women. The virus was only detected in them for eight days, whereas this was the case in the group of sick people for 19 days.

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