Submitted by No Soap Radio
On January 22nd China’s National Health Commission published guidelines (1) for the timely detection and reporting of new cases of SARS-CoV-2 or 2019-nCoV as it was known at the time, based on “WHO guidelines for the global surveillance of severe acute respiratory syndrome (SARS)”(2) and the “Consensus document on the epidemiology of severe acute respiratory syndrome (SARS)” (3). These documents described the median incubation period of SARS as 4-5 days with a range of 2-10 days, with isolated and not fully confirmed reports of values as large as 14. The consensus document does mention considerable debate about the 10-day maximum but moves on without any resolution beyond mentioning that further investigation is required. Based on this guidance, theNational Health Commission advised that case history should be linked to an event within 14 days before the onset of symptoms. These guidelines were in effect until sometime in early February.
This resulted in two important outcomes. First is that in a case where a patient presents with acute respiratory illness outside of Wuhan and has no discernible epidemiological link to the city or to another case within that 14-day window, it cannot be defined as a suspect case. In such a case the patient will not receive testing to confirm SARS-CoV-2 and, importantly, will only receive standard guidance and treatment. In the case of mild illness this likely would mean “go home and rest”. Whether this was a deliberate decision or simple failure to account for the possibility that the incubation period would differ between SARS and SARS-2, I leave to the reader to decide. It is, however, a simple way to keep initial numbers low in a country where saving face is imperative.
The second outcome was that this advice (from both China and WHO) was then used to determine the 14-dayquarantine period currently in use worldwide. The obvious result of this outcome is that infected but not infectious people are likely being let out of quarantine before their infection has passed, potentially allowing them to become infective as their viral titre increases (infected means the virus is present, detectable or not, infective means a person is capable of spreading the disease). It is important to note here that a person without a detectable level of virus will not spread the disease even if they are infected, this, however, does not mean they will remain this way as their viral load increases.
Following this publication of clinical guidance, on January 29th, researchers from the Chinese Centre for Disease Control and Prevention published an analysis of the epidemiological characteristics of SARS-2 (4). They analysed the demographic characteristic, exposure history, and illness timelines of the first 425 confirmed cases. Unfortunately, only 10 cases at the time had complete histories available and these 10 cases were all that was used to estimate the mean incubation period. To worsen matters, they found that the 95th percentile mark sat at 12.5 days (95% CI, 9.2 to 18), a cause for concern for a couple of reasons. The first is that it sits on the outer edge of what had previously been seen during the SARS epidemic, a clear indication that with such a small sample size further investigation is required. The second is that with its limited sample size, the estimate of 12.5 days sits far too close to the 14-day limit for comfort. But both these facts seem to have gone unnoticed or uncared for by everyone.
Admittedly I am no better than the experts, as previously I pointed out a similar incongruity but did not investigate further. Where it should have been picked up is in a still pre-published article that was referenced previously (5), in which the incubation period is described as ranging between 0 and 24 days. Of particular note is Table 1, where the severely ill and non-severely ill sub-populations both have a maximum range of 24 indicating that there were at least two cases with 24-day incubation periods of the 1099 examined. Whilst at this point in time it appears that the length of the incubation period has little to no effect on the severity of the disease it is vital in determining effective quarantine periods
The most obvious outcome of this is people who are possibly still infected and are about to become infective are being given the all clear to return to their communities all over the world. Furthermore, failure to consider transmission outside of the 14 days before the onset of symptoms can easily result in sources of infection going unnoticed. This means that potentially infectious cases can “slip the net” and continue spreading disease, enabling others to slip by and so on.
The other mistake authorities made is to assume that asymptomatic cases simply did not exist. in mid-January, a possible case of asymptomatic transmission was reported in Germany but was later clarified that the woman in question did in fact have mild symptoms. However, there have been increasing amounts of anecdotal data that asymptomatic cases can spread the virus and one of the first case descriptions involving asymptomatic transmission is now available (6). This is extremely important because the Diamond Princess off the coast of Japan currently houses 634 cases, of which 328 or 51.7% are asymptomatic (7). This would seem to indicate that for every person who gets sick, there is another walking around who is possibly capable of spreading the disease.
Now to be clear, the way disease manifests in environments like cruise ships or hospitals is often very different from out in the general public. More detail is provided in the section below, but the general thrust of the matter is that, given the tight and communal nature of these ships, disease tends to be transmitted extremely quickly via whatever avenues are available. Another issue is that because of the difference in demographic distribution compared to the general population (a disproportionately large number of cruise ship passengers are elderly, for instance) we should be very cautious in drawing inference from the ship. However, it is currently the only location where a significant number of the asymptomatic population has been tested and so is, frankly, the only number currently available. Even if the proportion was halved, that is, for every 2 people showing symptoms 1 more was positive but asymptomatic, that would be cause for worry. Assuming the viral titre of an asymptomatic case follows the same approximate progression as that of a symptomatic case, by my best estimate, there would be a little over 28,000 asymptomatic infected at this moment globally, with around 1,000 outside of China. I must stress, to my current knowledge, these are very rough numbers based off poor data, but these are the best available, at this time, to the general public.
Why Are so ManyAboard the Diamond Princess Sick?
Cruise ships are both a metaphorical and literal incubator of all kinds of communicable disease, a fact well known in the fields of public health and microbiology. The unique combination of a diverse (in the original sense of the word) assortment of travelers in crowded, semi-enclosed environment enables the rapid spread of disease. This is especially true given the casual and intimate nature of vacationing.What this means is that even if you grant the chance of a vacationer bringing an infection aboard to be the same as someone spreading it to their workplace or amongst their family (it’s actually higher because of the diversity), once it gets into the general population of the ship, its ability to spread is much higher than it would otherwise be. Direct person-to-person contact is not the only form of transfer that is aided by the conditions aboard a cruise ship. Spread via fomites (inanimate objects that can transmit disease to a new host) such as serving utensils, guardrails, and furniture that are in regular contact with a much greater number of people compared to off-ship and so provide more opportunities not only for contamination but also transmission. Another worrying factor are indications that viral titre in faecal samples is as high or higher than in nasopharyngeal (nose and throat) samples. This suggests that faecal-oral transmission is a significant risk factor. During the 2003 SARS outbreak the faecal-oral route was implicated in the spread of the disease to 321 people living at the Amoy Gardens apartment complex in Hong Kong. Any living situation with shared plumbing can be a risk factor and in the case of the cruise ship it is only adding another factor on top of all the others.
Given the above it would seem that the inevitability of our situation is finally being recognized by Western governments, with parts of Italy in lockdown and the CDC telling Americans to prepare for “significant disruptions” to their lives. No doubt our government’s desire to avoid any action that might appear racist or mean has resulted in half-measures being taken at every step up until now, behavior that is likely to continue into the future. Even if isolationist polices were enacted this very minute, it is likely that much of the West already has as yet unnoticed ongoing spread. I have mentioned in the previous piece about a few ways to keep clothing and surfaces sanitized and that advice has not changed. Over the coming weeks and months, we will likely see various areas of infrastructure put under stress. I would recommend that as much as possible people prepare themselves so that they are not reliant on it in the case it does fail.