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It Is an Isolated Incident That Is Unlikely It Will Repeat Again

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Background

On 27 May 2020, WHO published updated interim guidance on the clinical management of COVID-19,one,2 and provided updated recommendations on the criteria for discharging patients from isolation. The updated criteria reflect recent findings that patients whose symptoms have resolved may all the same examination positive for the COVID-xix virus (SARS-CoV-2) by RT-PCR for many weeks. Despite this positive test result, these patients are not likely to be infectious and therefore are unlikely to be able to transmit the virus to some other person.

This scientific cursory provides the rationale for the changes made to the clinical direction of COVID-19 guidance, based on recent scientific evidence.  WHO will update these criteria as more information becomes bachelor. For more information about clinical care of COVID-19 patients, see WHO's full guidance.i

Previous recommendation

Initial recommendation (published on 12 January 2020)

WHO'southward first technical package of guidance for the clinical direction of the novel coronavirus, now known as COVID-xix, was published in early Jan 2020, shortly after a cluster of atypical pneumonia cases was get-go reported in Wuhan, People'south Commonwealth of Cathay,three and included recommendations on when a patient with COVID-19 is no longer considered infectious.

The initial recommendation to confirm clearance of the virus, and thus allow discharge from isolation, required a patient to be clinically recovered and to have two negative RT-PCR results on sequential samples taken at to the lowest degree 24 hours autonomously.4 This recommendation was based on our knowledge and experience with similar coronaviruses, including those that cause SARS and MERS.five

Updated recommendation

New recommendation (published on 27 May 2022 every bit role of more comprehensive clinical care guidance1)

Within the Clinical Management of COVID-xix interim guidance published on 27 May 2020,one WHO updated the criteria for discharge from isolation equally part of the clinical care pathway of a COVID-19 patient. These criteria apply to all COVID-nineteen cases regardless of isolation location or disease severity.

Criteria for discharging patients from isolation (i.eastward., discontinuing transmission-based precautions) without requiring retesting[1]:

  • For symptomatic patients: 10 days after symptom onset, plus at least 3 boosted days without symptoms (including without fever [two] and without respiratory symptoms)[iii]
  • For asymptomatic cases[4]: 10 days after positive examination for SARS-CoV-2

For instance, if a patient had symptoms for 2 days, then the patient could exist released from isolation afterwards x days + three = thirteen days from engagement of symptom onset; for a patient with symptoms for 14 days, the patient can be discharged (14 days + iii days =) 17 days after date of symptom onset; for a patient with symptoms for 30 days, the patient tin exist discharged (30+3=) 33 days later symptom onset).

*Countries may cull to proceed to utilise testing as part of the release criteria.  If so, the initial recommendation of two negative PCR tests at to the lowest degree 24 hours autonomously can be used.

What is the reason for the change?

In consultations with global expert networks and Member States, WHO has received feedback that applying the initial recommendation of 2 negative RT-PCR tests at least 24 hours autonomously, in lite of limited laboratory supplies, equipment, and personnel in areas with intense manual, has been extremely difficult, especially outside hospital settings.

With widespread community transmission, these initial criteria for SARS-CoV-2 posed several challenges:

  • Long periods of isolation for individuals with prolonged viral RNA detection after resolution of symptoms, affecting individual well-being, society ,and admission to healthcare.13
  • Insufficient testing chapters to comply with initial belch criteria in many parts of the world.
  • Prolonged viral shedding around the limit of detection, having negative results followed by positive results, which unnecessarily challenges trust in the laboratory system.23-28

These challenges and newly available information on the adventure of viral transmission over the course of the COVID-xix affliction provided the framework for updating WHO'due south position on the timing of discharging recovered patients from isolation in and outside health care facilities. WHO continuously reviews scientific literature on COVID-19 through its Scientific discipline Partitioning and its COVID-nineteen technical teams. All aspects of clinical management of COVID-19 patients and laboratory testing strategies are discussed within WHO and with Member States and WHO's global expert networks of public health professionals, clinicians, and academics around the earth. These good networks and the Strategic and Technical Advisory Group for Infectious Hazards (STAG-IH)7 considered the challenges and reviewed the bachelor data in the decision process to change the initial recommendation.

The updated criteria for discharge from isolation balances risks and benefits; however, no criteria that can be practically implemented are without risk.  There is a minimal remainder chance that manual could occur with these not–examination-based criteria.  In that location tin be situations in which a minimal residual risk is unacceptable, for case, in individuals at loftier adventure of transmitting the virus to vulnerable groups or those in high-adventure situations or environments. In these situations, and in patients who are symptomatic for prolonged periods of time, a laboratory-based approach can yet be useful.

WHO encourages the scientific community to compile additional evidence to farther improve isolation belch criteria and establish the conditions under which isolation tin can be abbreviated or where the possible risks of the electric current discharge criteria require farther accommodation. Better understanding of manual risk amongst individuals with different clinical presentations or comorbidities and in different settings will assistance farther refinement of these criteria. For situations that might withal crave a laboratory-based approach, we encourage the further optimization of such a laboratory algorithm. WHO encourages countries to go on testing patients, if they accept the capacity to practice so, for systematic data collection that will raise understanding and better guide decisions nearly infection prevention and control measures, especially among patients with prolonged illness or those who are immunocompromised.

Current agreement of manual risk

Infection with the virus causing COVID-19 (SARS-CoV-2) is confirmed by the presence of viral RNA detected by molecular testing, usually RT-PCR.  Detection of viral RNA does non necessarily mean that a person is infectious and able to transmit the virus to another person. Factors that make up one's mind transmission take a chance include whether a virus is still replication-competent, whether the patient has symptoms, such as a cough, which can spread infectious droplets, and the behavior and environmental factors associated with the infected private. Usually v-10 days after infection with SARS-CoV-ii, the infected individual starts to gradually produce neutralizing antibodies. Binding of these neutralizing antibodies to the virus is expected to reduce the take a chance of virus transmission.10,xi,29,35

SARS-CoV-2 RNA has been detected in patients 1-3 days earlier symptom onset, and viral load in the upper respiratory tract peaks inside the first week of infection, followed past a gradual decline over time.ten,12,15,19,21,22,36-39 In the feces and lower respiratory tract, this viral load seems to peak in the second calendar week of affliction.nineteen Viral RNA has been detected in upper respiratory tract (URT) and lower respiratory tract (LRT) and carrion, regardless of severity of affliction.xix At that place seems to be a trend in longer detection of viral RNA in more severely ill patients.ten,14,15,18,19,41-43Studies of viral RNA detection in immunocompromised patients are limited, but one written report suggested prolonged detection of viral RNA in renal transplant patients.33 Some studies analyzed the take a chance of manual related to symptom of onset, and the estimated risk of transmission was highest at or effectually the time of symptom onset and in the first v days of affliction.13,15

The power of the virus to replicate in cultured cells serves as a surrogate marker of infectivity but requires special laboratory capabilities and may non exist as sensitive as PCR.10,20 Animal models tin can help understanding of manual risk. In a study by Sia, et al., hamsters infected with SARS-CoV-2 were housed with good for you hamsters on either solar day 1 or day 6 after infection. Manual to healthy hamsters occurred in the 24-hour interval 1 group, only not in those exposed 6 days after inoculation. In this model, the timing of transmission correlated with the detection of virus using jail cell culture, but non with detection of viral RNA in donor nasal washes.31

Studies using viral culture of patient samples to assess the presence of infectious SARS-CoV-2 are express.8-10,21,29,thirty,34Viable virus has been isolated from an asymptomatic case.9 A written report of nine  COVID-xix patients with mild to moderate disease institute no SARS-CoV-ii virus able to be cultured from respiratory samples after mean solar day 8 of symptom onset.10 Iii studies of patients with undisclosed or variable caste of disease showed an disability to culture virus afterward days seven-nine of symptom onset.viii,29,30  Patients who were RT-PCR positive on retesting after an initial negative RT-PCR on discharge from isolation were also studied, and none of these patients yielded positive viral cultures.29 One possible outlier is a case written report of a patient with mild COVID-19 who remained PCR-positive for 63 days after symptom onset. In this patient, viral cultures were positive from upper respiratory tract specimens just on the day of symptom onset, but were culture-positive from sputum samples until day 18.22 Information technology is unclear whether this posed a transmission risk as the patient had no respiratory symptoms. In a hospital-based report of 129 patients severely or critically ill with  COVID-19, 23 patients yielded at to the lowest degree one positive viral culture. This study included 30 patients who were immunocompromised. The median duration of viral shedding as measured by civilisation was 8 days post onset, the interquartile range was v-11, and the range was 0-twenty days.xi The probability of detecting virus in culture dropped below v% later xv.2 days after of symptoms. In this report, patients testing positive by viral civilization were still experiencing symptoms at the time of sample collection.11 This and other studies have described the correlation between reduced infectivity with the decrease in viral loads10,11,29,34 and a rise in neutralizing antibodies.ten,xi,29 Although viral RNA tin can be detected by PCR even after the resolution of symptoms, the amount of detected viral RNA is essentially reduced over time and generally beneath the threshold where replication competent virus tin exist isolated. Therefore, the combination of fourth dimension after onset of symptoms and the clearance of symptoms seems to be a generally safety arroyo based on electric current information.

Conclusion

Based on prove showing the rarity of virus that can be cultured in respiratory samples afterward ix days afterward symptom onset, peculiarly in patients with balmy disease, usually accompanied by rising levels of neutralizing antibodies and a resolution of symptoms, it appears condom to release patients from isolation based on clinical criteria that require a minimum fourth dimension in isolation of 13 days, rather than strictly on repeated PCR results. It is important to note that the clinical criteria require that patients' symptoms have been resolved for at least 3 days before release from isolation, with a minimum fourth dimension in isolation of xiii days since symptom onset.

These modifications to the criteria for discharge from isolation (in a health facility or elsewhere) remainder the understanding of infectious risk and the practicality of requiring repeated negative PCR testing, especially in settings of intense transmission or limited testing supplies. Although the run a risk of transmission afterward symptom resolution is likely to be minimal based on what is currently known, it cannot be completely ruled out. However, there is no zero-risk approach, and strict reliance on PCR confirmation of viral RNA clearance creates other risks (due east.g. straining resources and limiting access to health intendance for new patients with acute disease). In patients with severe affliction who are symptomatic for prolonged periods of fourth dimension, a laboratory-based approach might likewise aid determination-making on the demand for prolonged isolation. Such a laboratory-based approach tin can include measuring viral load and neutralizing antibiotic (or proven equivalent antibiotic) levels.10,xi,29 More research is needed to further validate such an approach.

WHO will update these criteria as more information becomes available. For more data nearly clinical intendance of COVID-nineteen patients, see WHO's full guidance.one

[1] Countries can choose to continue to use a laboratory testing algorithm every bit part of the release criteria in (a subset of) infected individuals if their take a chance assessment gives reason to do and then.

[2] Without the apply of any antipyretics.

[three] Some patients may experience symptoms (such as post viral cough) beyond the period of infectivity. Further research is needed. For more information about clinical intendance of COVID-nineteen patients, run across our Clinical Management Guidance.1

[4] An asymptomatic case is an individual who has a laboratory confirmed positive test and who has no symptoms during the complete form of infection.

References

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Criteria for releasing COVID-19 patients from isolation

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Source: https://www.who.int/news-room/commentaries/detail/criteria-for-releasing-covid-19-patients-from-isolation

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