The ongoing coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused immense global morbidity and mortality alongside devastating economic ramifications. In China, the authorities adopted sweeping measures to contain the virus, from lockdowns to compulsory hospitalization of every known case, regardless of symptoms, until two successive tests were returned negative. This policy aimed to prevent viral transmission from occurring once a case was identified.
Study: An unusual COVID-19 case with over four months of viral shedding in the presence of low neutralizing antibodies: a case report. Image Credit: joshimerbin / Shutterstock
However, a new study published in The Journal of Biomedical Research in November 2020 describes a case in which the standard diagnostic measures failed to achieve such containment of transmission. Despite this rigorous approach, the investigators came across a patient who was still shedding SARS-CoV-2 even after two consecutive tests turned out negative. The case came to light during a surveillance study, when a repeat test on the patient turned out to be positive.
The patient was a woman of about 68 years, admitted on January 21, 2020, with a four-day history of sore throat and a cough. She had been in Wuhan for 15 days before returning to her home city of Nanjing on January 16. There were no specific physical findings, and blood tests were also within normal limits.
Serology to influenza A and B showed the absence of IgM against these viruses, as well as for parainfluenza. HIV serology was negative. A CT of the chest showed a small characteristic ground-glass opacity in the right lower lobe of the right lung, and SARS-CoV-2 infection was confirmed by a reverse transcriptase-polymerase chain reaction (RT-PCR) performed on a throat swab. She continued to be monitored, and the viral load was measured on alternate days.
The patient was treated with combined antivirals, including aerosolized interferon-α at a dose of 5 million units twice a day, from January 22 to February 5, 2020, along with lopinavir/ritonavir, started a day later, for the same period. She also had intravenous immunoglobulin 20g a day for 5 days starting January 23.
Despite these therapies, her illness progressed. On January 25, she became febrile, and pneumonia spread throughout both lungs by January 27, leading to the initiation of methylprednisolone at 40mg a day for five days from January 28. This led to a marked clinical improvement.
By February 5, she had three negative tests, one after the other, resulting in her discharge the same day, at 19 days from the first symptom.
Repeated PCR positive
Following her discharge, she was quarantined at home, in a four-member household. On February 22, a throat swab was taken from her again by the local Center for Disease Control staff, with an inconclusive result. A repeat sample of induced sputum was taken the next day. This turned out to be PCR positive, at 37 days from the onset of symptoms.
The patient was completely asymptomatic, and her chest CT showed no signs of a relapse. Nonetheless, local CDC policy dictated that she be readmitted to the hospital because of the positive PCR test. She was monitored by both throat swab and induced sputum PCR, and aerosolized interferon-α was repeated at the same dose, along with arbidol and chloroquine phosphate for 2 weeks and 1 week, respectively. She remained asymptomatic and free of chest signs on CT, but sputum remained persistently positive for the viral RNA even on May 24, more than 4 months from symptom onset.
Her lymphocyte count at this time was normal, but the CD8+ T cell count was absolutely and relatively low throughout the illness. During her period of moderate to severe COVID-19, the lymphocyte count dropped still further, but increased in parallel with her clinical improvement.
On day 40 and day 43, her serum IgM was slightly elevated above baseline and became normal by day 73. Her IgG levels were a little higher but followed the same declining trend. A surrogate virus neutralization test (sVNT) was carried out for neutralizing antibody titer, and found the effective titer to be only 1:10 to 1:20.
On day 83, a cytokine analysis showed no evidence of infection or illness, with all tested cytokines like IL-2, IL-4, IL-6, IL-19, TNF-α and IFN-γ within normal limits. A sputum viral culture on April 28, meanwhile, turned out to be negative. This was day 102 from symptom onset.
The sputum finally tested negative from day 129 onwards, in 8 consecutive PCR tests, leading to her discharge on day 137 from symptom onset, still without any symptoms or clinical features.
Timeline summary of the two hospitalization events together with data of viral RNA detection. B: Contact tracing of family members and other results for viral RNA and antibodies. C and D: Results for antibody tests conducted on day 40, 43, 73, 83, and 100 post symptom onsets for IgM/IgG (C) and neutralizing antibodies (D). Testing for IgM and IgG was conducted at a serum dilution of 1:80 using ELISA kits from GenScript following the manufacturer's instructions.
Why did this happen?
The prolonged period of viral shedding, in this case, contrasts sharply with the median period of 17 days as estimated for Wuhan patients. However, in some cases, symptoms may come to an end, but viral shedding continues for up to 60 months, as described in some earlier studies. The current study, however, describes “the longest duration of SARS-CoV-2 viral shedding: for more than 4 months.”
What determines the period of viral shedding? Some have cited high temperature at admission, the time from the onset of symptoms to admission, and the length of hospitalization, as indicators of prolonged shedding. In the current study, this woman was febrile at presentation, and at admission, which occurred 4 days from symptom onset. She also had no comorbidities.
The only explanation offered is a potentially low IgG antibody titer, which may indicate that antibody therapy is essential in COVID-19 management. In fact, five patients with critical disease recovered with convalescent plasma therapy. This still does not tell us why this patient continued to shed the virus, even though she had received convalescent plasma containing high titers of neutralizing antibody.
Could reinfection have occurred, accounting for the late or repeated positive? The researchers think not, in the absence of new symptoms, failure to display IgM antibody rise after the second hospitalization, and lack of exposure since all her family members were negative for the virus.
Further studies will show if the viral RNA represents a dead or live infectious virus. One study indicates that the amount of infectious virus is very small, and cannot be isolated after 8 days from the onset. Moreover, none of her three household members were infected, nor did they develop antibodies, despite living with her for 2-3 weeks.
The researchers suggest, “Viral RNA shedding in the sputum of COVID-19 patients may last for over 4 months. Two consecutive negative nucleic acid tests may not be prerequisite for ending quarantine in [such patients].”