key: cord-0755164-c5q7l7en
authors: Rahimi, Farid; Bezmin Abadi, Amin Talebi
title: Challenges of managing the asymptomatic carriers of SARS-CoV-2
date: 2020-04-18
journal: Travel Med Infect Dis
DOI: 10.1016/j.tmaid.2020.101677
sha: 5a00336efd90e76d34de8c65cc27dda58631cf89
doc_id: 755164
cord_uid: c5q7l7en

Abstract After an outbreak in Wuhan, China, a growing number of countries are now suffering from an epidemic by SARS-CoV-2, which causes COVID-19. Undoubtedly, reports of the skyrocketing global spread of COVID-19 has shocked people globally, from Japan to the United States.Presently, the World Health Organization indicates that fatality due to COVID-19 is about 2%, inferring that many positive subjects may potentially overcome the illness with mild influenza-like symptoms and no need for hospitalization at intensive-care units. Because COVID-19 is completely new to the human immune system, many throughout the world are likely vulnerable to becoming sick after their initial exposure to SARSCoV-2. Besides hospitalized cases, many individuals are likely asymptomatic but potentially carry the virus. While our knowledge about carriers and their virus shedding is deficient, some studies modelling the viral transmission have considered the potential contribution of the asymptomatic carriers. Protocols for managing asymptomatic cases, for example for controlling them to restrict their contact with healthy people at public places or private residences, have not been established.In-house quarantine may as well be applicable to asymptomatic cases if they could be identified and diagnosed. Presumably now, the asymptomatic subjects potentially contribute to the transmission of COVID-19 without their knowledge, intention or being diagnosed as carriers. Thus, managing the asymptomatic cases, who can carry and likely transmit the virus, is a major healthcare challenge while a pandemic is looming.

Dry cough, fever, lymphopenia, malaise, diarrhea, and dyspnea are the predominant signs and symptoms of COVID-19. The primary symptoms may last up to 14days after exposure, and the incubation period ranges 9-12days. Untreated disease may result in alveolar damage and pneumonia, mostly culminating in organ failure and death. The major route of interpersonaltransmission is through temporal and physical close contact with patients (by aerosols through sneezing or coughing).This was confirmed when some nurses who cared forhospitalized patients were found positive,while having no history of visiting the seafood markets at Wuhan[2], the origin of the pandemic. Before strict quarantine measures were implemented in Wuhan, positive cases were rationally thought to originate afterhuman-human transmission, instead of zoonotic transmission, in densely populated markets. However, the exact means of viral transmission is stillnot fully understood [3] , especially in the initial cases. Indeed, investigation of the naturalbackground of the virus as a putative zoonotic disease is important for preventing future outbreaks.

Besides hospitalized or confirmed cases, many asymptomatic individuals potentially carry the virus. Thus, diagnosing the patients and finding the asymptomatic carriers will help us understand the exact viral transmission routes.Simulation studies can mathematically modelthe contribution of the asymptomatic carriers in person-person viral transmission [4] , highlighting thatfulminating cases are unlikely to be the only viral sources. Reportedly, the viral load in an asymptomatic carrier is akin to that in a symptomatic patient; thus, asymptomatic or minimally symptomatic patientsare likelyto transmit the virus as well as symptomatic patients. They could likely freely shed the virus into the environment,potentially boosting the transmission cycle as an unintentional, but dangerous, viral source. Asymptomatic carriers are thus likely to participate, more than symptomatic cases, in mass-gatherings, sporting events, shopping, and going to schools or gyms. The asymptomatic carriers may have been rapidly spreading the virus within, and to, many different countries.We postulate that the increase in the number of affected countries 10-20 days after the initial reports of the outbreak may have been partially facilitated by the asymptomatic carriers. Crowd masking has been suggested to prevent the transmission of the virus to healthy uninfected people,and this could also prevent the asymptomatic carriers from shedding the virus. On 2 March 2020, an expert WHO team travelled to Tehran and aimed to investigate the viral transmission dynamics and at-risk populations. Such surveys help grow our experience on how to control COVID-19 globally. Recently, China, Bahrain, Jordan, the United States, Afghanistan, Italy, Australia, and South Korea temporarily closed their borders to decrease the viral spread. Nevertheless, cohesive guidelines on how to manage the asymptomatic carriers are lacking. Local screening and surveillance of the asymptomatic carriers by simple PCR-based assayscould be effective in managing the viral transmission by the carriers. A limitation of sampling could be that oropharyngeal or nasopharyngealswabs may fail to result in confirmatory diagnosis of an asymptomatic carrier, and deeper sampling of the respiratory tract may be necessary.

In conclusion, data on asymptomatic carriers acting as potential viral transmitters are scarce. No confirmatory or contradictory reports on the case-fatality rate or revised incubation period of COVID-19 have emerged from the involved countries, including North America, Europe, Australia, and Africa.Thus, our understanding of pathogenesis, transmission, carriers, virus shedding,and incubation period of COVID-19 and its complex interaction with the host immune system is mostly incomplete. We acknowledge that the highest priority by the world decisionmakers is to defeat the pandemic,but concurrently, intervening with, and screening the asymptomatic carriers should be considered worldwide before a second large wave of positive cases emerges.The lessons learned from the present COVID-19 pandemic are that 1) robust research endeavors are required to change our mindset about emerging pathogens; and 2) surveillance and screening systems should be recruited for monitoring the less-known viral or bacterial pathogens.

Declarations Travel Medicine and Infectious Disease requires that all authors sign a declaration of conflicting interests. If you have nothing to declare in any of these categories then this should be stated.

A conflicting interest exists when professional judgement concerning a primary interest (such as patient's welfare or the validity of research) may be influenced by a secondary interest (such as financial gain or personal rivalry). It may arise for the authors when they have financial interest that may influence their interpretation of their results or those of others. Examples of potential conflicts of interest include employment, consultancies, stock ownership, honoraria, paid expert testimony, patent applications/registrations, and grants or other funding.

No conflict of Interest.

All sources of funding should also be acknowledged and you should declare any involvement of study sponsors in the study design; collection, analysis and interpretation of data; the writing of the manuscript; the decision to submit the manuscript for publication. If the study sponsors had no such involvement, this should be stated.

No fund was received.

Print name Farid Rahimi

Manuscript number (if applicable): Article Title: Challenges of managing asymptomatic individuals exposed to SARS-CoV-2

Author name: Farid Rahimi, Amin Talebi Bezmin Abadi

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