COVID-19 News: New Research Alarmingly Shows That Mildly Symptomatic COVID-19 Individuals Can Be Contagious For Longer Periods
: Brazilian scientists have in a new study reported two cases of individuals with SARS-CoV-2 shedding infectious virus for a significantly longer period than has previously been reported. The findings can also implications on quarantine periods etc.
Previously, it has been estimated that individuals with COVID-19 can shed replication-competent virus up to a maximum of only twenty days after initiation of symptoms. This report describes two patients with mild forms of the disease who shed replication-competent virus for 24 and 37 days, respectively, after symptom onset.
The study findings were published on a preprint server and are currently being peer reviewed. https://www.medrxiv.org/content/10.1101/2020.11.18.20232546v1
Corresponding author Dr Maria Cassia Mendes-Correa from the Institute of Tropical Medicine-Sao Paulo told Thailand Medical News, “It has been estimated that individuals with COVID-19 can shed replication-competent virus up to a maximum of twenty days after initiation of symptoms. To the best of our knowledge, there are no previous reports of replication-competent virus being isolated three weeks after symptom onset.”
The study team says that the findings suggest that individuals with mild symptoms can remain infectious for prolonged periods, highlighting the need for them to take appropriate precautions to avoid spreading the virus to others.
Ever since the COVID-19 outbreak in Wuhan, China, late 2019 research has indicated that SARS-CoV-2 can be detected among infected individuals 1 to 3 days before developing symptoms.
It was found that viral load then peaks during the first week of symptom onset before gradually declining over time.
Past research have estimated that replication-competent virus is no longer present in COVID-19 patients 20 days following symptom onset.
However, this estimate has come from studies that have mostly involved hospitalized individuals and those with severe disease, says co-researcher Dr Antonio Sesso from the University of São Paulo.
Dr Sesso said, “Studies to address the possible presence of SARS-CoV-2 during the different phases of COVID-19 disease in mildly infected individuals, and utilization of viral culture techniques to identify replication-competent viruses, have been limited.”
The study team showed that in two SARS-CoV-2-infected women with mild disease, the SARS-CoV-2 coronavirus was shown to be replication-competent for longer than has previously been reported.
The women had participated in the Corona São Caetano Program, an initiative offering primary care for COVID-19 to all residents of São Caetano do Sul.
Individuals living in the municipality were encouraged to complete a questionnaire if they developed symptoms consistent with COVID-19. Individuals who met the criteria for suspected COVID-19 were contacted and asked to complete a risk assessment. Individuals who met the triage criteria for mild disease were offered a home visit where they could provide a nasopharyngeal swab for analysis.<
Of the two clinical cases, the first case (case 1) was a woman in her 50s who reported in mid-April that she had first experienced a dry cough, headache, loss of strength, joint pain, and muscle pain, but no fever, 20 days previously.
Twenty-two days following symptom onset, the woman had a nasopharyngeal swab taken that tested positive for SARS-CoV-2.
Alarmingly, the woman then developed nausea, vomiting, and a loss of taste and smell. Significant symptoms persisted, and 37 days following symptom onset, a second nasopharyngeal swab tested positive for the virus.
Despite the woman was still reporting a mild headache and loss of strength in mid-May, most symptoms gradually resolved.
The other woman (case 2), also in her 50s, reported experiencing fever, headache, sore throat, cough, loss of strength, joint pain, muscle pain, discharge of nasal fluids, and nausea at the beginning of May.
A COVID-19 nasopharyngeal swab test taken five days following symptom onset tested positive for SARS-CoV-2. After symptoms continued to persist, a second nasopharyngeal swab was taken 24 days following symptom onset, which showed that the woman was still infected. Case 2 remained symptomatic for around 35 days following onset.
Dr Sesso further added, “Due to the persistence of symptoms and a prolonged positive RT-PCR result, it was decided to investigate the replicative capacity of their SARS-CoV-2 virus.”
The test samples obtained from case 1 on day 37 and from case 2 on day 24 were inoculated into Vero CCL81 cells, and diagnostic tests were performed on the supernatant.
Interestingly In both cases, cytopathic effects were observed in the cell culture supernatants and the presence of replicating SARS-CoV-2 was confirmed by real-time reverse transcriptase-polymerase chain reaction (RT-PCR).
The study team said, “Cytopathic effects were observed in the Vero cell cultures incubated with samples from both patients after three passages and the presence of replicating SARS-CoV-2 in culture supernatants was confirmed by real-time RT-PCR. In addition, by electron microscopy, aggregates of elongated and spheroid particles ranging in size from around 60 nm to140 nm with peripheral spike-like projections consistent with the morphology described for SARS-CoV-2 (9) were observed. The major and minor axes of the virus profiles were 100 and 58 nm, respectively. Measurements of the orthogonal long and short axes of several virus particles, located close to two cells in the same preparation had the following mean dimensions with the corresponding standard error of the mean, respectively, 90 ± 4.5 nm (n=22) and 62 ± 5.1 nm (n=22). Viral particles were seen mainly at the cell periphery and eventually inside cytoplasmic vacuoles.”
The World Health Organization (WHO) recommendations regarding the criteria for discharging SARS-CoV-2-positive individuals from isolation is that patients must be clinically recovered and symptom-free, say the researchers.
The study team warns, “Our data reinforce that even mildly symptomatic individuals are potentially contagious.”
The researchers say further clarification of the frequency of presumed prolonged infectivity will be defined by prospective follow-up studies involving a more significant number of individuals.
Dr Sesso concluded, “Nevertheless, this report highlights that individuals with prolonged but mild symptoms can remain positive for the replication-competent virus, highlighting the need for such individuals to exercise appropriate precautions to avoid potential transmission of SARS-CoV-2 in their community.”
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