Results
In the first investigation, we aimed to test whether viral positive can be found in anal swab and blood as well as oral swabs. We conducted a molecular investigation to patients in Wuhan pulmonary hospital, who were detected as oral swabs positive for 2019-nCoV upon admission. We collected blood, oral swabs and anal swabs for 2019-nCoV qPCR test using previously established method [5].
We found 15 patients who still carry virus following days of medical treatments. Of these patients, 8 were oral swabs positive (53.3%), 4 were anal swabs positive (26.7%), 6 blood positives (40%) and 3 serum positives (20%). Two patients were positive by both oral swab and anal swab, yet none of the blood positive was also swabs positive. Not surprisingly, all serum positives were also whole serum positive (Table 1). In summary, viral nucleotide can be found in anal swab or blood even if it cannot be detected in oral swabs. It should be noted that although swabs may be negative, the patient might still be viremic.
Table 1. Molecular detection of 2019-nCoV in swabs and blood. Samples were from oral swabs (OS), anal swabs (AS) and blood. Data were shown as qPCR Ct values. Patients in severe condition during investigation were shown.
  OS AS Whole blood Serum Severe disease
Patient 1 33.5       No
Patient 2     30.3 24.3 Yes
Patient 3 30.3       No
Patient 4     32.1   No
Patient 5   33.1     No
Patient 6     30.6   No
Patient 7 32.7 30.2     No
Patient 8   33.1     No
Patient 9     31.4 34.5 No
Patient 10     30.9 33.0 Yes
Patient 11 27.3       No
Patient 12 34.4       Yes
Patient 13 32.9 33.6     No
Patient 14 32.3       No
Patient 15     31.6   No
We then did another investigation to find out the dynamic changes of viral presence in two consecutive studies in both oral and anal swabs in another group of patients. The target patients were those who received around 10 days of medical treatments upon admission. We tested for both viral antibody and viral nucleotide levels by previously established method [5]. We showed that both IgM and IgG titres were relatively low or undetectable in day 0 (the day of first sampling). On day 5, an increase of viral antibodies can be seen in nearly all patients, which was normally considered as a transition from earlier to later period of infection (Figure 1 and supplementary table 1). IgM positive rate increased from 50% (8/16) to 81% (13/16), whereas IgG positive rate increased from 81% (13/16) to 100% (16/16). This is in contrast to a relatively low detection positive rate from molecular test (below).
Figure 1. Serological detection of 2019-nCoV. Dashed line indicates cutoff, which was determined based on data from healthy controls.
For molecular detection, we found 8 oral swabs positive (50%) and 4 anal swabs (25%) in these 16 people on day 0. On day 5, we were only able to find 4 oral swabs positive (25%). In contrast, we found 6 anal swabs positive (37.5%). When counting all swab positives together, we found most of the positives came from oral swab (8/10, 80%) on day 0. However, this trend appears to change on day 5. We found more (6/8, 75%) anal swab positive than oral swab positive (4/8, 50%). Another observation is the reoccurrence of virus in 6 patients who were detected negative on day 0. Of note, 4 of these 6 viral positives were from anal swabs (Table 2). These data suggested a shift from more oral positive during early period (as indicated by antibody titres) to more anal positive during later period might happen.
Table 2. Molecular detection of 2019-nCoV in swabs from two investigations. Samples were from oral swabs (OS), anal swabs (AS) and blood. Data were shown as qPCR Ct values.
  Date 0-OS Date 0-AS Date 5-OS Date 5-AS
Patient 1     23.2  
Patient 2 30.3      
Patient 3   19.5    
Patient 4 32.7 30.2    
Patient 5   33.1    
Patient 6 31.1   30.0 31.4
Patient 7 27.3      
Patient 8     27.0  
Patient 9 32.9 33.6    
Patient 10       23.8
Patient 11 31.9      
Patient 12 32.3      
Patient 13       17.8
Patient 14       25.5
Patient 15       30.0
Patient 16 33.8   26.9 27.5