Covid-19: 10% of infected are still contagious 10 days later

A small study conducted in England indicates that a minority of people infected with SARS-CoV-2 retain traces of viral activity ten days after the initial infection.

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Isolated a sick person is to limit the risk that it contaminates another. With l’epidemic from Covid-19, most of us have experienced at least a period of isolation after being contact case or infected. The arrival of variant Omicron pushed the government to adapt the isolation measures, now the initial quarantine can last up to ten days for an unvaccinated positive person. At the end of these ten days, the person is considered non-contagious and can break their isolation. But is this really the case?

Scientists from the University of Exeter, England, carried out tests PCR individuals, who amplifyARN sub-genomic, on samples collected in 2020. According to their results, 13% of those tested still show significant amounts of subgenomic RNA after 10 days.

Traces of active replication in 13% of people studied after 10 days

The replication from genetic material from coronavirus, a single-stranded, positive-sense RNA strand, is complex. The proteins non-structural are produced directly from RNA genomics. While the structural proteins (the spike, the envelope, the membrane and the nucleocapsid) are produced from other molecules of RNA, absent from virion initial but made during replication, called subgenomic RNAs (or sgRNAs).

Scientists were able to analyze the evolution of the amount of sgRNA

Unlike routine PCRs, which are not able to tell the difference between a viable virion or not, the study of subgenomic RNAs makes it possible to know if viral replication is active in a patient and therefore, if he is potentially contagious. The presence of sgRNAs of uncomfortable E was detected in 72 of the 176 patients included in the study. The scientists were able to analyze the evolution of the quantity of sgRNA for 32 patients from this group. For four of them, or 13%, the amount of sgRNA exceeds 1,000 copies/mL between 11 and 31 days after their last screening. For these individuals, coronavirus replication appears to still be ongoing after ten days. The scientists identified one individual in which the sqRNAs were still present after 68 days.

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« This means that these individuals are likely to have remained contagious beyond 10 days and could have transmitted the virus to others », explains Professor Lawrence Young, a virologist at the University of Warwick.

This small study should not be over-interpreted. If the presence of sgRNA is evidence of a still active viral cycle, this does not automatically mean that the person is truly infectious. There are other methods, more difficult to implement but also more reliable, to quantify the infectious virions in a sample. Additionally, the study was done in 2020, when the Delta or Omicron did not circulate and that there was no vaccine. « His findings really apply to the original Wuhan virus. The other variants Alpha, Delta and Omicron more transmissible probably result in more than 10% of infections still active after 10 days », concludes Dr. Julian Tang, from the University of Leicester.

17% of patients who have had Covid-19 are still carriers of the virus

Article published on October 30, 2020 by Céline Déluzarche

People already with Covid-19 were thought to be quiet for at least a few months. This is not the case: not only do many of them still experience symptoms after their healing, but 17% are again positive for coronavirus and therefore potentially contagious. This discovery, even if it is not reserved for Covid-19, nevertheless calls into question the isolation protocols.

At the end of October, more than 45 million people worldwide have been affected by the coronavirus, of which 32.9 million of them are considered cured. There is however “long” forms of Covid-19 where patients still suffer from breathing difficulties, severe fatigue, aches or from loss of smell sometimes for several months after recovery. Others case of re-infection have also been described. A new study published in the journal American Journal of Preventive Medicine shows today that nearly 17% of former Covid-19 patients are still carriers of the virus, sometimes long after.

The study was conducted by the foundation Agostino Gemelli University Hospital, in Rome (Italy), where a multidisciplinary health service has been created for patients who have recovered from Covid-19 in order to establish a follow-up of the sick after recovery and to assess the impact of the virus on their body . For the study, 131 people officially declared cured were tested again and, for 16.7% of them, the test RT-PCR again tested positive.

Persistent symptoms unrelated to the presence of the virus

Positive or negative, most of the patients were doing rather better and none of them showed fever. However, many of them presented persistent symptoms, although of lesser intensity than during the acute phase of the disease: fatigue, 51%; breathing difficulties, 44%; cough, 17%. Curiously, the prevalence of these symptoms is similar between people who tested negative and those who tested positive, which means that this criterion is not a good predictor of infectiousness.

Notable rate of recovered Covid-19 patients may still be asymptomatic carriers of the virus

« Our findings indicate that a notable rate of recovered Covid-19 patients may still be asymptomatic carrierss you virus, warns Franceso Land, lead author of the study. The question that still needs to be answered to contain the pandemic from Sars-CoV-2 is whether the persistent presence of fragments of the virus means that patients are still infectious. The RT-PCR test looks for small fragments of viral RNA. A positive swab can reveal whether patients continue to shed virus fragments, but cannot discern whether or not they are infectious ».

A clue, however: no positive case has been recorded in their entourage, which pleads for a low infectivity. When in doubt, the authors still recommend that people considered cured to continue to apply barrier gestures, such as wearing a mask or washing hands.

PCR tests: a false confidence index

The persistence of symptoms after illness is not unique to Covid-19, however. It is known that after a pneumonia for example, many patients continue to experience breathing difficulties. The Lyme disease, caused by a tick bite, also gives rise to long forms. Finding traces of virus long after infection is also not unusual. A 2017 study has, for example, found traces of Zika virus RNA in patients who have been cured for months.

The Italian study above all reflects the weaknesses of the RT-PCR tests, which are nevertheless considered as a reference: not only can they give rise to false positives or false negatives, which falsifies the studies, but they do not indicate in nothing if the virus is still active or if it is ” waste remaining in the body or whether the person remains infectious or not.

The coronavirus would stay longer in the body of severely affected patients

Article by Julien Hernandez published on 04/23/2020

According to a recent retrospective study, SARS-CoV-2 remains longer in the body of patients with a severe form of the disease than in that of moderately affected patients. Additionally, the peak of the viral load would also last longer in this type of patient. Caution, however, as this study has limitations.

The SARS-CoV-2 pandemic has already contaminated more than 2.5 million people in the world. To stem the epidemic and therefore the contagiousness of carriers, it is essential to know how the viral load evolves in infected patients. A recent study published in the British Medical Journal gives some clues that will have to be confirmed.

Its objective was to assess the progression of the viral load according to the severity of the disease. 96 patients were admitted in the data analysis, 74 severe and 22 moderate. The sample is small and disproportionate, which can lead to possible biases. More than 3,497 different samples (mucus, in this, serum, urine) were collected from patients. Here is what scientists have observed and what they conclude.

Viral load and disease severity

First, the patients in this cohort with a severe form of the disease keep the virus longer in their bodies (duration median 21 days) than moderate cases (median 14 days). Then the peak of the viral load, that is to say the moment when it peaks because the virus replicates enormously, also lasts longer in these patients.

Indeed, the peak is observed during the second week in moderate cases, then fades while it remains high during the third week of the disease in severely affected patients. Finally, the authors note that the virus is present for a much longer period in stool of patients (median duration of 22 days) than in their secretions respiratory (median duration of 18 days), regardless of the gravity of the disease.

What should we think of these observations?

They must be taken for what they are, that is to say observations. The study has limitations, in particular the fact that it is not multicentric and that sample size is insufficient. The authors acknowledge this themselves: This can lead to an unbalanced distribution of confounders when assessing viral shedding and viral load. » Then, the viral load is influenced by many factors.

The quality of the samples taken directly affects viral load, so the study of viral load only partially reflects the amount of virus in the body. Finally, les tests PCR cannot distinguish between viable and non-viable virus, and does not reflect the level of virus replication in different tissues. We must therefore be careful with these preliminary results and not draw hasty conclusions.

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