Viral shedding patterns of coronavirus in patients with probable severe acute respiratory syndrome

Abstract

Severe acute respiratory syndrome (SARS) is thought to be caused by a novel coronavirus, SARS-associated coronavirus. We studied viral shedding of SARS coronavirus to improve diagnosis and infection control. Reverse-transcriptase PCR was done on 2134 specimens of different types. 355 (45%) specimens of nasopharyngeal aspirates and 150 (28%) of faeces were positive for SARS coronavirus RNA. Positive rates peaked at 6-11 days after onset of illness for nasopharyngeal aspirates (87 of 149 [58%], to 37 of 62 [60%]), and 9-14 days for faeces (15 of 22 [68%], to 26 of 37 [70%]). Overall, peak viral loads were reached at 12-14 days of illness when patients were probably in hospital care, which would explain why hospital workers were prone to infection. Low rate of viral shedding in the first few days of illness meant that early isolation measures would probably be effective.

The Immunobiology of SARS

“…Quantitative studies of viral shedding in SARS patients provide some hints into the pathogenesis of the disease. Compared with other respiratory viral infections, such as influenza, SARS had a longer incubation period (mean 4.6 days, variance 15.9 days) (25), and the viral load in the upper respiratory tract, including nasopharyngeal aspirates and throat swabs, was low during the first 4 days and peaked at 10 5.8 copies/mL in nasopharyngeal aspirates 10 days after the onset of disease (19, 86,87). However, nasopharyngeal viral titers did not always accurately reflect viral load in the lungs.…”

“…However, nasopharyngeal viral titers did not always accurately reflect viral load in the lungs. Viral load in the lower respiratory tract, including bronchoalveolar lavage, sputum, and endotracheal aspirates, was higher than in the upper airways (86,88). Virus was detected in multiple tissues at autopsy, including the lungs, intestine, liver, kidneys, brain, spleen, and lymph nodes (21, 23, 57, [89][90][91][92][93].…”

Molecular Epidemiology of Severe Acute Respiratory Syndrome–Associated Coronavirus Infections in Taiwan

“…Because this is the first documented case in which there is molecular proof of transmission on a train, it raises the question of why only 1 passenger contracted the infection. Because it has been reported that SARS appears to be most infectious at 6-11 days after onset of illness and not during the first day of symptoms [29], we assumed that the visitor from Amoy Gardens was not highly infectious during the train ride, even though he developed symptoms during the same evening that he traveled from Taipei to Taichung.…”

Diagnosis and pharmacotherapy of severe acute respiratory syndrome: what have we learnt?

“…Shedding of SARS-CoV, evaluated by RT-PCR on 2,134 nasopharyngeal aspirates and faeces, shows positive rates, peaking at 6-11 days after the onset of illness for nasopharyngeal aspirates (58-60%) and 9-14 days for faeces (68-70%). Overall, peak viral loads were reached at 12-14 days of illness [5]. Therefore, antiviral therapy should be instituted in the early phases of the illness to coincide with this time frame.…”