Recombinomics Commentary 16:30
March 13, 2013
Fortunately, he added, the virus is "very difficult to acquire."
Dr. Susan Gerber, a medical epidemiologist in the CDC's Division of Viral Diseases, agrees.
There's no evidence of sustained human-to-human transmission, she said, "where you see a chain of many cases going person to person to person."
"People shouldn't freak out," she added. "There's no evidence that this virus is easily spread, say, across a room."
The above comments on nCoV human to human (H2H) are largely based on negative data which lacks credibility. There have been three lab confirmed clusters, and all three clusters include symptomatic contacts who tested negative. Moreover, in the largest cluster, most of the symptomatic cases were designated as probable cases, based on interviews with symptomatic health care workers and relatives.
Most of the key detail (disease onset dates and relationships between probable cases), has been withheld for the ICU cluster in Jordan last April. However, local media reports and WHO updates indocate that the cluster involved at least 12 people, including 2 doctors, 7 nurses, and two family members of health care workers (HCWs). Outbreaks at ICU’s of a rare mysterious disease are usually linked to a treated patient, as was seen in the SARS-CoV outbreak in March of 2003. Like the current nCoV, SARS-CoV was present at higher levels in the lower respiratory tract and detection in the upper respiratory tract was a challenge. Moreover HCWs were at risk because the hospitalized cases had severe infections and coughing or intubation procedures could spread the virus “across a room”. The key signature of the SARS spread was super-spreaders, who could infect many contacts, who were typically HCWs.
WHO has not explained why the survivors in the ICU cluster were not lab confirmed, but the failure may be linked to a low level of virus in samples collected from the upper respiratory tract. However, they did acknowledge that the symptomatic cases were probably infected, as were at least two family members who cared for the HCWs. Disease onset dates were not released, but the two fatal case (45F nurse and 25M intern) died a week apart, suggesting the disease onset dates supported an extended transmission chain.
The extended transmission chain was also supported in the familial cluster in Riyadh, although WHO also withheld disease onset dates for that cluster. The index case (70M) was said to have developed symptoms in “October”. One of his sons (39M) was hospitalized after his father’s death, and the son’s disease onset date was October 28. His brother’s (31M) disease onset date was between November 3-5, supporting a transmission chain from the father to the older brother to the younger brother. A fourth family member tested negative, but was also classified as a probable case due to common symptoms and contact with the three confirmed cases.
H2H transmission was also supported in the UK cluster. The index case (60M) developed symptoms while performing Umrah in Saudi Arabia. Three family members developed symptoms in the UK, and the two confirmed cases had no travel outside of the UK in the weeks prior to disease onset. The son (39M) died, but the other confirmed family member (30F), who had a mild case, had no contact with the son, and contact with the index case was limited to three hospital visits. However, since the index case was on an ECMO machine it is unlikely that the nCoV was transmitted at the hospital. A fourth family member was a likely link between the index case and the two additional confirmed case, but that family member also tested negative.
Thus, the claims of “no evidence” for sustained transmission is heavily dependent on false negatives in symptomatic cases that were characterized as probable, and claims of no transmission “across a room” a just another media myth.
