You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family's personal health.
You should not use it to replace any relationship with a physician or other qualified healthcare professional. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult your physician or, in serious cases, seek immediate assistance from emergency personnel. Contact Us Online. What is viral shedding? Viral shedding and masks Because a person infected with a respiratory virus is shedding virus particles from their nose and mouth, you can quickly conclude that a mask will decrease the spread of viral particles as they are physically trapped by the mask.
Two additional aspects of masking are worth considering in the context of viral shedding: A mask also protects the person who is wearing it — Because a mask serves as a physical barrier, it offers some protection for the person wearing it. However, people can inadvertently expose themselves if they touch a contaminated mask or other surface and then touch their eyes, nose or mouth. So, a mask worn by an infected person offers more protection than a mask worn by an uninfected person because the net result is fewer infectious viral particles circulating in the air and landing on surfaces.
Said another way, if you are healthy and susceptible and you find yourself in a situation with one mask and an infected person, give them the mask and physically distance. You will be safer than if you wear the mask yourself. The type and fit of the mask is important — Given that a mask serves as a physical barrier for virus particles, the type of material from which the mask is made and the snugness of its fit are important determinants of its effectiveness.
This is why multilayer masks made of materials with tight fibers are more effective, and bandanas and gaiter masks are less effective. You can find information on how to properly wear, remove and care for your mask in this previous Parents PACK article. Viral shedding and vaccines Viral shedding can occur following vaccination if the vaccine contains live, weakened viruses because that type of vaccine causes immunity through viral reproduction.
Parts of virus — During an infection, the entire virus is produced, but the COVID vaccines only introduce the nucleic acid related to one viral protein — the spike protein — so no other genes or proteins are available to produce viral particles.
Simply put, it is impossible for the vaccines to result in the production of infectious virus particles. Our cells do not have the directions to make the whole virus. Location of processing — As described earlier, when a person is infected with COVID, the earliest viral replication occurs in the nasal cavity. If the immune system does not gain control during those early days, the virus may spread to other parts of the body and infect cells in other locations.
This is why some people seem OK in the beginning, but then after about a week, they get more severely ill. On the other hand, the mRNA and adenovirus-vector vaccines are processed near the injection site, so the spike protein is never in an area of the body from which it could be shed, such as the nose. Whisper-down-the-lane game — Unfortunately, because there is confusion related to whether the virus can be shed after vaccination, other misinformed ideas become conflated with the idea that a vaccinated person is shedding the virus — or even just the spike protein.
The dataset from this study is held securely in coded form at ICES. The full dataset creation plan and underlying analytic code are available from the authors upon request, understanding that the computer programs may rely upon coding templates or macros that are unique to ICES and are therefore either inaccessible or may require modification.
Funding: This work received no direct funding support. The analyses, conclusions, opinions, and statement expressed herein are those of the authors, and not necessarily those of CIHI. There are no patents, products in development or marketed products associated with this research to declare.
With modelling from similar respiratory viruses as the only available guide [ 1 ], SARS-CoV-2 infectivity was initially assumed to resolve within 14 days of symptom onset. Subsequent research on molecular detection using real-time reverse transcriptase PCR RT-PCR suggested that SARS-CoV-2 shedding begins 2 to 3 days prior to symptom onset and continues for 7 to14 days [ 2 — 9 ], but for up to 20 to 31 days with more severe infection [ 4 , 5 , 10 — 12 ].
This evidence lacked external validity as almost all studies had been conducted in single settings, and were limited to hospitalised patients. Reliability was also difficult to determine as most lacked peer review [ 3 , 6 — 8 , 10 ], specimen sources varied [ 1 — 4 , 8 ], and sample sizes were small. In a different US study, the median duration of viral shedding as measured by time from a positive PCR to the second of two negative tests among patients was That study tracked those with repeat positive or negative tests and computed a documented shedding estimate based on continuing positivity of 15 days.
None of the studies referenced above were population-based and, with two exceptions [ 14 , 15 ] they excluded censored cases those that do not have a shedding resolution time. Robust, population-level evidence regarding the duration of viral shedding as measured by RT-PCR, whether it varies with age, sex, socioeconomic status, illness severity, or co-morbidities is lacking. Such information could be a useful step in understanding the link between viral shedding and infectivity [ 16 , 17 ] and the utility of PCR testing for re-infection.
This study describes the duration of RT-PCR-tested SARS-CoV-2 detection, henceforth referred to as viral shedding, using laboratory reports from the entire population of Ontario, Canada among individuals who had follow-up testing after an initial positive finding. We also assess variability in the duration of shedding by known determinants of health in general, such as age, sex, socioeconomic status, residence in long-term care LTC , and selected chronic conditions.
OLIS includes information on specimen source e. Postal codes of home addresses linked to census data were used to assign area-level socioeconomic status. Only patients with specimens taken from the upper or lower respiratory tract were included. All datasets were linked using unique encoded identifiers and were analysed at ICES. Date of onset of viral shedding was assigned as the day of a first positive RT-PCR test as this was available and more definitive than self-reported date of symptom onset, particularly for those with no symptoms.
Duration was calculated using the same approach taken by Agarwal et al [ 14 ]. Our use of the documented shedding estimate reduced selection bias by allowing inclusion of those patients whose testing ceased generally because of death, symptom resolution, or the end date of the study without definitive negative findings.
Study follow-up was truncated on May 31, Ambulatory care patients were identified as non-LTC residents with no hospital admission during the study period. Hospitalised patients were anyone hospitalised for any reason during their follow-up time. Chronic conditions asthma, congestive heart failure, chronic obstructive lung disease, hypertension and diabetes were identified via established prevalent disease cohorts at ICES created using validated algorithms applied to health administrative data.
Socioeconomic status was assessed using area-level income quintiles at the census dissemination level geographic units of to persons. Deaths occurring any time between a first positive test and May 31, , were tracked for subset reporting. Overall study population characteristics are described. We also compared those characteristics by whether or not patients contributed to the documented resolution and documented shedding estimates.
Statistical comparisons were made using standardised differences [ 19 ], z-tests and chi-square tests. We also report results for those who died versus the rest and for those diagnosed up to March 31, to assess whether longer follow up would yield longer estimates. To document the amount of information we had available, we report the number and percent positive tests performed for each follow up day in an S1 Appendix.
We assessed differences in time to documented resolution and documented shedding by age, sex, socioeconomic status, LTC residency, hospitalisation status and selected chronic conditions using multivariable quantile regressions computed at the 25 th , median, and 75 th percentiles.
As only anonymised administrative data were used the REB waived any requirement for consents. From the first available positive test on February 22, , until April 30, , there were 16, Ontario residents who tested positive for SARS-CoV-2 on either a nasal or throat swab. Excluded from this study were the 8, who were not retested, 1, who had insufficient testing to assign one of our two duration estimates most because there was only one negative result after the first positive or were non-residents of Ontario.
This resulted in a study population of 6, The number of tests per day and the percent positive on each day is reported in the S1 Appendix for all study participants and separately for those contributing to the documented shedding and documented resolution durations. Repeat testing was performed on between and patients for each follow-up day, with the largest numbers of repeat tests occurring on days 13 tests through 22 tests.
Their average age was Noting all relevant groups for each patient, which is why percentages do not total , Overall, 5. Table 1 also presents descriptions of those contributing to each of the shedding duration estimates, comparing those subgroups to the remainder of the study population. Of the 6, patients in this study, 1, Focussing on standardised differences above 0. The documented shedding group were also more likely to be male than the remainder More of those documented shedding patients died during the study period compared to the remainder 6.
The group contributing to the documented resolution estimate i. The documented resolution group were also less likely to be male than the remainder Fewer of these documented resolution patients died during the study period compared to the remainder 1.
Fig 1 presents smoothed density plots showing shedding duration distributions for those with two negative follow-up COVID tests documented resolution and those without such resolution documented shedding. Table 2 reports summary statistics for the documented shedding and documented resolution durations by selected subgroups. Compared to the whole study population, LTC residents had longer documented shedding and documented resolution durations medians of 23 and 29 days compared to 19 and 25 , and fewer individuals with documented shedding durations of less than 15 days Patients who were hospitalised, were in the ICU or were seen in the ED had longer documented resolution durations medians of 29, 30 and 28 days respectively versus 25 days and fewer individuals who were in the ICU or ED had durations of less than 15 days 2.
New England Journal of Medicine. The Journal of Infectious Diseases. Nature Medicine. Duration and key determinants of infectious virus shedding in hospitalized patients with coronavirus disease COVID Nature Communications. Nasopharyngeal SARS-CoV-2 viral loads in young children do not differ significantly from those in older children and adults. Sci Rep. Feb 4 ;11 1 Clin Infect Dis.
Nov 3 ;doi Pediatr Infect Dis J. Dec ;39 12 :ee Euro Surveill. Aug ;25 32 doi Emerging infectious diseases. Oct ;26 10 Jul 1 ;73 1 May 5 ;doi Journal of Medical Virology. Clinical Infectious Diseases. Available at SSRN Findings from Investigation and Analysis of re-positive cases. May 19, Accessed May 19,
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