The latest report from Chinese scientists that the coronavirus – officially named Covid-19 – incubation period may stretch to 24 days is being met with skepticism by the World Health Organisation (WHO).
The study, conducted by infectious diseases expert Zhong Nanshan, found that the median incubation period across 1,099 Chinese patients was 3 days.
The longest recorded incubation period was 24. The shortest was 0, according to The Straits Times (ST).
The Chinese study did not state how many patients supposedly experienced unusually long incubation periods.
According to ST, the study was uploaded as an unpublished manuscript and has not been peer reviewed.
Peer reviewing is defined as the “evaluation of work by one or more people with similar competences as the producers of the work”.
Peer reviewing is a common practice in which independent academics and researchers rate the ‘value’ of unpublished papers. Its purpose is to allow members of a field to self-regulate in the interest of maintaining credibility and improving quality standards.
MedRxiv, the site hosting the Chinese study, is an online archival repository of academic papers. According to ST, the site stated that papers uploaded are just preliminary works.
Consequently, the site considers these papers unverified. They recommend that clinical practice or treatment should therefore not be guided by them.
WHO has stated that they are not considering a change to their quarantine guidelines, despite the new study.
According to ST, Singapore’s Ministry of Health has echoed WHO’s sentiments. In particular, they note that the 24-day figure is an outlier. It could be due to errors, faulty research, or bias in the study’s methodology.
Dr Michael Ryan is the executive director of the WHO’s Health Emergencies Programme. He has explained that unusually long incubation periods may be erroneous reports.
Citing previous studies of Ebola by WHO, he said:
We’ve seen very long incubation periods and then when we investigate, we find that there was a second exposure a week later, or 2 weeks later, and that’s when the actual infection occurred.
Double exposure is when a patient is exposed to the virus twice, but only catches it on the second occasion.
For example, he might come into contact with an infected person on a Monday, but not catch the virus. Then a week later, on the following Wednesday, he finally catches it from another infected person.
The time between the first exposure and the actual date of infection would artificially inflate the incubation period. In this case, it would appear to be 10 days longer than it really is.
Dr Ryan emphasised how important it was to therefore be skeptical about extreme outliers. Extreme figures like the 24-day incubation period could very easily mislead policy and cause unnecessary alarm.
The concern caused by news reports of the unverified study have since only evinced this.
According to ST, respiratory viruses usually have incubation periods of 2 to 14 days. Notable examples include SARS and MERS-CoV — the 2 other notable coronaviruses in recent memory.
On a more positive note, WHO reports that 168 countries globally now possess the technology to identify the virus. Amongst that number is Singapore, which has produced its own homegrown test kit, courtesy of A*STAR.
To aid in virus relief efforts in China, Singapore sent 10,000 test kits to affection regions on Saturday (8 Feb).
With any amount of luck, it’ll make enough of an impact to turn the tide against this ordeal. In the meantime, we should all remain steadfast and do our part to help each other.
More information will be available later this year.
New makan places coming up soon!
Play with your kids for the upcoming school holidays.
An important reminder to take care of our health.
The mess took 3 hours to clean up.
No more awkward encounters at the cashier?