Covid-19: identifying and isolating asymptomatic people helped eliminate virus in Italian village
BMJ 2020; 368 doi: https://doi.org/10.1136/bmj.m1165 (Published 23 March 2020) Cite this as: BMJ 2020;368:m1165Read our latest coverage of the coronavirus outbreak
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Dear Editor
The authors present an interesting perspective on the large implications in the fight against the Coronavirus Disease 2019 (COVID-19) pandemic.
Health care workers need protection from COVID-19 patients. Similarly, non-COVID patients too need protection from COVID-19 positive healthcare workers, who although asymptomatic are likely to spread the infection to unsuspecting patients.
Considering that the RCPT test is only 60% positive and the rapid antibody test is only at a 30% sensitivity a question arises as to "how frequently would asymptomatic healthcare workers need to be tested"?
A more sinister observation could be that personal protective equipment (PPE) is not an efficient barrier against the SARS-Co-2 virus virulent contagion. This could have serious consequences if not addressed properly. Especially upon surgeons and operating room teams who perform urgent and emergency operations from COVID-19 and rationally conserve the PPE they wear https://www.sages.org/recommendations-surgical-response-covid-19/ .
Competing interests: No competing interests
Dear Editor
There is increasing evidences on a considerable proportion of asymptomatic infections in different contexts around the world, including asymptomatic sailors from a coronavirus-affected aircraft carrier (https://www.npr.org/2020/04/09/831266852/with-warship-coronavirus-cases-...), asymptomatic carriers in a Tibetan Autonomous Prefecture of China (medRxiv preprint; https://doi.org/10.1101/2020.03.27.20043836), and asymptomatic pregnant women who delivered infants at the New York–Presbyterian Allen Hospital and Columbia University Irving Medical Center (NEJM; April 13, 2020. DOI: 10.1056/NEJMc2009316).
Therefore, it is desperately needed to share the world with the previous response “Personal view on the divergence on the extent of asymptomatic infections with covid-19” (https://www.bmj.com/content/368/bmj.m1165/rr-2, posted online 07 April 2020) as soon as possible. Then, it will reduce or remove misunderstanding between the WHO report and a variety of findings and meanwhile increase mutual understanding and mutual support as well as unity amid COVID-19 global pandemic.
Competing interests: No competing interests
Dear Editor
My husband and I are retired pathologists and moved to South Texas about 2 years ago.
So far there are no or occasional positives, from travelers. Our city McAllen is in strict isolation from 2 weeks ago.
I wonder if we are in the situation that Dr Romagnani describes for Veneto. It would be so good if everyone here were tested.
Anyone interested in coming over to check us out? There is a hospital waiting for cases but so far nothing has materialized.
Competing interests: No competing interests
Dear Editor,
The death rate due to Covid-19 is greater (approximately 40%) in the infected elderly population ranging in age from 70 to 89 (1). In contrast with infected adults, the majority of children are asymptomatic or with mild symptoms. In Italy, as of April 6, a total of 2050 children and adolescents (0-19 years) were infected (1.3%) without any deceased (1). However, it has become clear that even children can die from Covid-19 infection as reported in some European countries and in the United States by press and media.
Current First Aid procedures for children and adults with Covid-19 positive swab showing mild symptoms plan to send them home in isolation. This procedure is not without risk as they can infect parents and grandparents, and also the family doctor called for a further medical examination. The number of asymptomatic subjects infected by Covid-19 is not known. A recent survey in Vo’Euganeo, near Venice, Italy, showed that the great majority of people infected with Covid-19 (50-75%) were asymptomatic, but represented “a formidable source” of contagion (2). In particular, asymptomatic children should be considered as plague spreader free to infect more vulnerable people, such as the elderly population, playing a major role in community-based viral transmission. Therefore, if children are important in viral transmission and amplification, social and public health policies could be established to slow transmission and protect vulnerable populations (3).
To date, 13,522 (mean age 48, 10% of the total, males 33%) doctors and healthcare personnel are infected by Covid-19 (1). Ninety-six doctors who had worked on the front lines in hospital or as family doctors have died of Covid-19 (4). Moreover, 6549 nurses (52% of the total healthcare personnel working in hospital) are infected. Twenty-six nurses have died; two of them, a 49-year-old and a 34-year-old who were Covid-19 positive, committed suicide because they feared that they had inadvertently spread the infection.
At present, doctors and healthcare personnel are not routinely tested for Covid-19, so that many of them can infect other subjects both in the hospital and during home visits. Furthermore, personal protective equipment for doctors and healthcare personnel are gradually running out and they are forced to prolong their use; the same face guard is used for many days because no replacement is available. Nevertheless, they are continuing to work.
In addition to quarantine, to reduce the spread of Covid-19 infection is mandatory to isolate as much as possible the asymptomatic and paucisymptomatic infected children avoiding interaction with elderly people, who are the population at greatest risk for Covid-19 infection and death; only one parent should assist his/her child until healing. A second important aspect is to protect doctors and healthcare personnel with adequate personal protective equipment which are currently in short supply.
A large use of nasopharyngeal swab for Covid-19 can be a valid method to detect rapidly the carrier of Covid-19 in the asymptomatic children population and in all healthcare personnel but this is not done. In addition to the social distance and the accurate use of personal protective equipment, it should be mandatory to rapidly identify the plague spreader in order to reduce the risk of getting infected.
"...at the beginning of the Covid-19 epidemic someone, including some doctors and virologists, said it was just a slightly more severe form of flu..."
References
1. Istituto Superiore di Sanità, https://www.epicentro.iss.it/
2. Day M. Covid-19: identifying and isolating asymptomatic people helped eliminate virus in Italian village. BMJ. 2020 Mar 23;368:m1165. doi: 10.1136/bmj.m1165.
3. Kelvin AA, Halperin S. COVID-19 in children: the link in the transmission chain. Lancet Infect Dis 2020; Mar 25. pii: S1473-3099(20)30236-X. doi: 10.1016/S1473-3099(20)30236-X.
4. National Agency for Social Security and Medical Assistance. www.enpam.it
Competing interests: No competing interests
Dear Editor
In addition to Romagnani’s findings that the majority infections with covid-19 (50-75%) were asymptomatic in Italy, [1] early data from covid-19 testing in Iceland suggested that about 50% of positive SARS-CoV-2 cases showed no symptoms, [2] and other studies like testing on the Diamond Princess cruise ship and testing on Japanese evacuees from Wuhan indeed found a significant number of asymptomatic infections. [3] These findings appeared to contradict the WHO report based on covid-19 situation in China. [1]
The Chinese covid-19 Emergency Response Epidemiology Team reported that asymptomatic cases accounted for below 2% of all the confirmed cases, [4] whereas some models estimated that more than 50% of infections were undocumented within China in which the people might experience self-limited and mild or no symptoms and thus be unrecognized. [5,6]
In general, factors like climate and geography seem insufficient to cause such a contradiction.
Furthermore, it is possible but less likely that with the rapid spread of covid-19 across the world, some of the novel coronaviruses have already evolved to become significantly less pathogenic (namely, causing much more mild or asymptomatic cases), markedly different from the coronavirus circulating in China.
Finally, it is most likely that the great majority of asymptomatic or subclinical infections have been removed “silently” from circulation after the implementation of stringent epidemic control measures to block covid-19 transmission (namely, Level-1 public health emergency response throughout China) for more than one month, such as staying at home as much as possible and wearing face masks when needed to go out. So the WHO report seems plausible, “the proportion of truly asymptomatic infections is unclear but appears to be relatively rare and does not appear to be a major driver of transmission in China”.
Currently covid-19 epidemic in China is under control. Nevertheless, widespread serological (antibody) tests are essential to assess how many people have been infected with SARS-CoV-2 previously and recovered, providing key data to better understand the epidemiology of covid-19.
References
1 Day M. Covid-19: identifying and isolating asymptomatic people helped eliminate virus in Italian village. BMJ 2020;368:m1165. doi:10.1136/bmj.m1165.
2 Iceland lab's testing suggests 50% of coronavirus cases have no symptoms. CNN 2020 April 3. https://edition.cnn.com/2020/04/01/europe/iceland-testing-coronavirus-in....
3 Qiu J. Covert coronavirus infections could be seeding new outbreaks. Nature 2020; published online 20 March. doi:10.1038/d41586-020-00822-x.
4 The Novel Coronavirus Pneumonia Emergency Response Epidemiology Team. The epidemiological characteristics of an outbreak of 2019 novel coronavirus diseases (COVID-19) — China, 2020. China CDC Weekly 2020;8:113-22. http://weekly.chinacdc.cn/en/article/id/e53946e2-c6c4-41e9-9a9b-fea8db1a....
5 Li R, Pei S, Chen B, Song Y, Zhang T, Yang W, et al. Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV2). Science 2020; published online 16 March. doi:10.1126/science.abb3221.
6 Wang C, Liu L, Hao X, Guo H, Wang Q, Huang J, et al. Evolving Epidemiology and Impact of Non-pharmaceutical Interventions on the Outbreak of Coronavirus Disease 2019 in Wuhan, China. medRxiv preprint 2020; posted 06 March. https://doi.org/10.1101/2020.03.03.20030593.
Competing interests: No competing interests
Dear Editor
We are told very clearly that there is very little benefit to members of the general public from wearing a simple face mask. However WHO currently recommends that people should wear face masks if they have respiratory symptoms
https://www.thelancet.com/journals/lanres/article/PIIS2213-2600(20)30134-X/fulltext
Surely if asymptomatic carrier transmission is important we should all wear masks in case we are asymptomatic carriers - along with all the other recommended measures. The only exceptions would be those who have been definitely diagnosed with Covid 19 and recovered.
Which countries have done well with Covid 19? China and South Korea. One used strict lockdown one didn’t - both have a very high citizen use of masks. Could this possibly be one significant factor in their progress so far?
Competing interests: No competing interests
Dear Editor,
This commentator has yet to acquire Italian as another language, so the insights that follow might have already been considered in the original piece, if so, apologies in advance. Risk of repetition aside:
The problem with blanket testing, especially of an isolated village of 3,000 people, is that even with very good tests the possibility of false positives remain high. Assuming for the moment that nobody has the virus at issue in the village (0 in 3,000 prevalence) and the test is 90% sensitive and 90% specific. Then of those three thousand, 2,700 will come back accurately as negative, but 300 would come back as positive despite the patient not having the virus. If we alter the sensitivity and specificity to 95%, 2,850 will come back accurately as negative, but 150 will come back as falsely positive. If we alter this yet again, making 98% the sensitivity and specificity, 2,940 will be accurately identified, but 60 will be false positives. This is simply because the test is imperfect. It is unclear to this commentator the actual sensitivity and specificity of the tests involved, nor is the prevalence in the village known.
Of course, if one were to serially repeat these tests on this population, they would not come out with mathematical precision each time. It would vary and could have more false positives on one measurement, but less on the next. This problem affects all low-prevalence disease testing. One must be mindful of this when it comes to blanket testing in isolated areas, or anywhere for that matter.
So the possibility exists that those tested who were asymptomatic, might not have had the virus at all. And that the difference on the repeat measurement was just what happens in the World of Small Numbers.
Irrespective of this point, the bottom-line recommendations of isolation and the full suite of measures remain sound.
Competing interests: No competing interests
Dear Editor,
In sciences dealing with compartment fire and fire hazards, flashover stands for a near-simultaneous ignition of the combustible material in a compartment. After flashover, the temperature promptly increases, rising to its maximum value in a Gaussian fashion. Flashover depends on the size of the room, burning materials, heat release rate of each material, threshold temperature (auto ignition temperature), and so on. Mathematical comparison can be drawn between flashover’s spatial pattern variation and the current COVID-19 worldwide spread.
During fire, the air moves and increases heat transfer; in the same way, people move and spread the disease. Flashover is not mandatory for fire: it depends on the materials involved. This is the case in disease, where the mean age of people stands for the type of burning material: if people are old or sick the likelihood increases. Even taking into account additional parameters (such as geographic location, occurrence of airports, number of swabs performed, etc.), things are similar, making the problem of a COVID-19 flashover a painstaking issue.
A worldwide flashover is not an imminent danger, however compartment flashover (in a country) might be unfortunately the case. What happens if nobody puts in regulations? Will COVID-19 spread behave like fire, possibly leading to a catastrophic local flashover? Therefore, it’s time to restrict people’s spreading: with additional regulations to prevent crowd movements and individual contacts, flashover can be prevented.
Flavia-Corina Mitroi-Symeonidis
Police Academy "Alexandru Ioan Cuza", Fire Officers Faculty, Bucharest, Romania.
Academy of Economic Studies, Department of Applied Mathematics, Bucharest, Romania.
fcmitroi@yahoo.com
Ion Anghel
Police Academy "Alexandru Ioan Cuza", Fire Officers Faculty, Str. Morarilor 3, Sector 2, Bucharest RO-022451, Romania.
ion.anghel@academiadepolitie.ro
Arturo Tozzi
Center for Nonlinear Science, Department of Physics, University of North Texas, Denton, Texas, USA
tozziarturo@libero.it
Arturo.Tozzi@unt.edu
Competing interests: No competing interests
A growing body of evidence for a considerable proportion of asymptomatic infections
Dear Editor
Now, it is of interest to note that a recent population-based sero-epidemiological survey of seroprevalence of antibodies to SARS-CoV-2 in Wuhan, China, found 6.92% of a cross-sectional sample of the population in Wuhan developed antibodies against SARS-CoV-2 (namely, positive for pan-immunoglobulins against SARS-CoV-2), with 39.8% of this population seroconverting to have neutralising antibodies, and importantly, 82.1% of this population (positive for pan-immunoglobulins) were asymptomatic.1
Reference
1 He Z, Ren L, Yang J, Guo L, Feng L, Ma C, et al. Seroprevalence and humoral immune durability of anti-SARS-CoV-2 antibodies in Wuhan, China: a longitudinal, population-level, cross-sectional study. Lancet 2021; 397: 1075–84. DOI:https://doi.org/10.1016/S0140-6736(21)00238-5
Competing interests: No competing interests