A Confirmed Asymptomatic Carrier of 2019 Novel Coronavirus

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A Confirmed Asymptomatic Carrier of 2019 Novel Coronavirus

Background and Study Context

The emergence of the 2019 novel coronavirus (2019-nCoV) in December 2019 led to a global public health crisis, characterized by rapid transmission and diverse clinical presentations. A significant proportion of confirmed cases (approximately 40%) initially presented without symptoms but later developed coronavirus disease-2019 (COVID-19). While presumed asymptomatic transmission had been suggested in earlier reports, no confirmed cases of persistent asymptomatic carriers had been documented prior to this study. This paper presents the first confirmed case of an asymptomatic 2019-nCoV carrier, identified through rigorous epidemiological and clinical investigations in Anhui Province, China.

Study Design and Methodology

The study was part of the Epidemiological Study of 2019-nCoV Infection in Anhui, which utilized standardized case report forms adapted from the International Severe Acute Respiratory and Emerging Infection Consortium/World Health Organization protocol. Data collection included symptom onset, epidemiological links, healthcare visits, hospitalization details, treatment regimens, laboratory results, and clinical outcomes.

All suspected and confirmed cases in Anqing City were hospitalized at Anqing Municipal Hospital. Data were extracted from medical records, cross-verified by independent investigators, and validated through physician consultations. Chest computed tomography (CT) scans were reviewed by two licensed radiologists, with consensus interpretations adopted.

Confirmation of 2019-nCoV Infection
Diagnosis followed stringent guidelines from China’s National Health Commission, requiring two consecutive positive real-time reverse transcription polymerase chain reaction (RT-PCR) tests using distinct nucleic acid detection kits. Anhui Province implemented a two-step confirmation protocol:

  1. Municipal Testing: Initial testing at municipal Centers for Disease Control and Prevention (CDC) laboratories using two kits, with cross-checked results.
  2. Provincial Validation: Positive samples were retested at the Anhui Provincial CDC laboratory using the same methodology. Only cases validated at both levels were confirmed as positive.

Case Identification and Clinical Findings

By February 21, 2020, 83 confirmed 2019-nCoV cases were identified in Anqing. Eight cases were asymptomatic at confirmation, seven of whom later developed symptoms. Patient A, a 50-year-old woman, remained asymptomatic throughout 17 days of hospitalization, representing the first confirmed asymptomatic carrier.

Epidemiological Context

Patient A resided with her husband (Patient B) and had no travel history to Wuhan or exposure to wildlife. The infection cluster originated from Patient E, a Wuhan traveler who transmitted the virus to Patient D (Patient B’s brother) during a work interaction on January 21. Patient D subsequently infected his wife (Patient C) and brother (Patient B). Key timeline events include:

  • January 26: Patient D developed fever.
  • January 30: Patient C developed fever.
  • February 5: Patients C and D tested positive for 2019-nCoV.
  • February 6: Patients A and B tested positive despite being asymptomatic.

Clinical and Laboratory Observations

Patient A

  • Initial Presentation (February 6): No symptoms (afebrile, normal respiratory rate, SpO₂ 99%). Chest CT showed no abnormalities.
  • Hospitalization (February 6–23): Remained asymptomatic with stable vital signs (temperature ≤36.8°C, SpO₂ ≥97%).
  • Laboratory Results:
    • February 7–20: White blood cell counts (4.2–6.25 ×10⁹/L), lymphocyte counts (1.2–1.6 ×10⁹/L), and CRP (4.1–32.1 mg/L) fluctuated within or near normal ranges.
    • February 20: Elevated alanine aminotransferase (90 IU/L) and aspartate aminotransferase (62 IU/L), attributed to lopinavir/ritonavir treatment.
    • Viral Persistence: Throat and anal swabs remained RT-PCR-positive on February 19 and 21.

Patient B (Husband)

  • Initial Presentation (February 6): Asymptomatic but with ground-glass opacity on chest CT.
  • Clinical Course: Developed intermittent low-grade fever (≤37.5°C) from February 7–13.
  • Outcome: Throat and anal swabs turned negative by February 22.

Treatment and Management

Patient A received:

  • Antiviral Therapy: Aerosolized interferon-α2β (February 6–16) and lopinavir/ritonavir (200 mg/50 mg twice daily for 10 days).
  • Post-Day 10: Intravenous ribavirin (0.5 g every 12 hours).
  • Hepatoprotective Measures: Glycyrrhizinate initiated on February 20 for elevated liver enzymes.

Despite treatment, viral RNA persisted in respiratory and anal specimens, suggesting limited efficacy of the antiviral regimen. Patient B received similar therapy, with corticosteroids added for mild symptoms.

Key Implications and Discussion

  1. Asymptomatic Carriage and Transmission Risk

    • Patient A’s persistent viral positivity without symptoms highlights the potential for asymptomatic individuals to act as reservoirs for community transmission.
    • The epidemiological link between Patients A, B, D, and E demonstrates transmission during the asymptomatic phase, underscoring the challenge of containment without proactive surveillance.

  2. Diagnostic and Monitoring Considerations

    • Anal Swab Testing: Persistent viral RNA in anal swabs (despite respiratory samples remaining positive) supports fecal-oral transmission risks, necessitating expanded testing protocols.
    • Imaging Limitations: Normal chest CT findings in asymptomatic carriers emphasize the need for RT-PCR as the diagnostic gold standard.

  3. Therapeutic Challenges

    • The lack of symptom resolution or viral clearance with lopinavir/ritonavir and ribavirin aligns with emerging evidence questioning their efficacy in mild or asymptomatic cases.
    • Drug-induced hepatotoxicity (observed in Patient A) warrants caution in antiviral use for asymptomatic carriers.

  4. Public Health Recommendations

    • Targeted Surveillance: Close contacts of confirmed cases require RT-PCR testing regardless of symptom status.
    • Vaccine Development: The case strengthens the urgency for vaccines to prevent asymptomatic spread.
    • Isolation Policies: Asymptomatic carriers may require prolonged isolation until consecutive negative tests are achieved.

Conclusion

This study provides the first confirmed evidence of a persistent asymptomatic 2019-nCoV carrier, with implications for pandemic control strategies. The case illustrates the virus’s ability to transmit during pre-symptomatic and asymptomatic phases, complicating traditional containment measures. Persistent viral shedding in respiratory and gastrointestinal tracts necessitates revised testing and isolation guidelines. While therapeutic options for asymptomatic carriers remain limited, the findings underscore the critical role of epidemiological vigilance and the need for rapid vaccine deployment to mitigate silent transmission chains.

doi:10.1097/CM9.0000000000000798

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