key: cord-1018123-4gaa14ly authors: Ge, Yang; McKay, Brian Kenneth; Sun, Shengzhi; Zhang, Feng; Handel, Andreas title: Assessing the impact of a symptom-based mass screening and testing intervention during a novel infectious disease outbreak: The case of COVID-19 date: 2020-02-23 journal: nan DOI: 10.1101/2020.02.20.20025973 sha: ae6fc64042b050df93ebb8f8045892952f18510f doc_id: 1018123 cord_uid: 4gaa14ly A symptom-based mass screening and testing intervention (MSTI) can identify a large fraction of infected individuals during an infectious disease outbreak. China is currently using this strategy for the COVID-19 outbreak. However, MSTI might lead to increased transmission if not properly implemented. We investigate under which conditions MSTI is beneficial. part of containing infectious disease outbreaks [1, 2] . A symptom-based mass screening and 23 testing intervention (MSTI), is an approach that can identify a significant fraction of infected 24 individuals. In the current novel coronavirus (COVID-19) outbreak, China is using an MSTI 25 strategy in an attempt to identify as many cases as possible [3] . While the concept of identify, 26 isolate, and treat is not new in terms of controlling an outbreak [4] the scales at which it is 27 currently being used is. A problem for a situation such as the COVID-19 outbreak is that many 28 novel pathogens show symptoms that are similar to common infections, e.g., general respiratory 29 symptoms. Since general respiratory symptoms are common, a MSTI can quickly overload the 30 health system [5] . Strained health facilities mean reduced care for individuals with other health 31 needs. In addition, such a situation might directly lead to a worsening of the outbreak, due to 32 increased transmission at testing sites [6, 7] . We explore how the latter risk affects the potential 33 benefit of MSTI. 34 We consider a scenario where a novel pathogen has entered a population and causes symptoms 35 that are non-specific and similar to circulating pathogens, e.g., general respiratory symptoms. 36 . CC-BY-NC-ND 4.0 International license It is made available under a author/funder, who has granted medRxiv a license to display the preprint in perpetuity. is the (which was not peer-reviewed) The copyright holder for this preprint . https://doi.org/10.1101/2020.02.20.20025973 doi: medRxiv preprint The default is to ask individuals with symptoms to stay home and follow general precautionary 37 measures [8] . An alternative option is to implement MSTI, which requires testing anyone with 38 symptoms specific for the novel pathogen at a healthcare facility. individual is infected with the novel pathogen (probability ), we assume that they are correctly 49 identified and placed under isolation and treatment, where they have reduced transmission and 50 mortality risks, namely and . Importantly, if the health system is strained, those patients 51 arriving at the testing facility without being infected with the novel pathogen (probability 1 − ) 52 may become infected by another person in the testing facility. We denote this probability of 53 becoming infected with . Since these individuals test negative, we assume they will be sent 54 home and then have the same transmission and mortality risk as individuals asked to remain at 55 home. Thus, the total transmission potential for a person undergoing screening is = + 56 (1 − ) and the total mortality risk is = + (1 − ). 57 . CC-BY-NC-ND 4.0 International license It is made available under a author/funder, who has granted medRxiv a license to display the preprint in perpetuity. is the (which was not peer-reviewed) The copyright holder for this preprint . https://doi.org/10.1101/2020.02.20.20025973 doi: medRxiv preprint = / = / + (1 − ) / and = / = / 0 + (1 − ) / . If that 59 expression is less than 1, it suggests that MSTI reduces transmission and mortality. If it is larger 60 than 1, the better strategy would be to not implement MSTI. 61 As a best-case scenario, we consider a situation where isolation and treatment following a While hard numbers for the quantities and for specific pathogens or outbreaks are 86 impossible to obtain, we used previously published data to obtain very rough estimates for and 87 ranges for the COVID-19 outbreak, as well as the 2014 Ebola outbreak and a combination of 88 previous measles outbreaks (see SM for details). Those estimates are shown as colored areas in 89 the figure. For both measles and COVID-19, our estimates suggest that depending on the specific 90 . CC-BY-NC-ND 4.0 International license It is made available under a author/funder, who has granted medRxiv a license to display the preprint in perpetuity. is the (which was not peer-reviewed) The copyright holder for this preprint . https://doi.org/10.1101/2020.02.20.20025973 doi: medRxiv preprint setting (e.g. a specific country), MSTI might or might not be beneficial. It seems more clearly 91 beneficial for Ebola, mainly due to Ebola-related symptoms that make the disease easier to 92 discriminate from other pathogens, thus leading to a higher . 93 For MSTI to be beneficial, one needs to minimize and maximize [9] . An approach to reduce 94 could be the use of dedicated testing sites separate from the usual healthcare facilities [10] . 95 Staff at those sites can be trained to follow protocols that reduce transmission risk. One could 96 also ask symptomatic individuals to call a phone number and schedule a test, instead of allowing 97 individuals to self-report at any time. With a scheduling system, crowding can be reduced, and 98 when individuals show up at the scheduled time, they can be processed rapidly, thus reducing 99 transmission risk [6] . 100 can be increased by having a more specific case definition (ideally without losing sensitivity). 101 This would reduce the overall pool of individuals with symptoms and increases among those 102 targeted for testing. More refined case definitions, screening by experts using telemedicine 103 approaches [11], or rapid home tests [12] could all be options which reduce the pool of those 104 considered at risk of being infected with the novel pathogen, thus increasing . This will also 105 reduce the total number of individuals going to testing sites, likely reducing . 106 Overall, our analysis suggests that MSTI can be useful if the probability of transmission at 107 testing sites is less than the probability that a symptomatic person is infected with the novel 108 pathogen. Both and will likely vary between settings and thus should be evaluated for a 109 specific setting, e.g. a specific country, if MSTI is considered as a potential control strategy. 110 . CC-BY-NC-ND 4.0 International license It is made available under a author/funder, who has granted medRxiv a license to display the preprint in perpetuity. is the (which was not peer-reviewed) The copyright holder for this preprint . https://doi.org/10.1101/2020.02.20.20025973 doi: medRxiv preprint Factors that make an infectious disease 112 outbreak controllable Comparing nonpharmaceutical interventions for 114 containing emerging epidemics Transcript of the press conference on February Health Commission of the People's Republic of China Accessed 5 When is quarantine a useful control strategy for 121 emerging infectious diseases? How to maintain surveillance for novel 123 influenza a h1n1 when there are too many cases to count Potential for airborne transmission of infection in the 125 waiting areas of healthcare premises: Stochastic analysis using a monte carlo model Transmission characteristics of mers and sars in the 128 healthcare setting: A comparative study Interventions for the interruption or reduction of the 130 spread of respiratory viruses Evaluation of the benefits and risks of 132 introducing ebola community care centers, sierra leone Health care facility and community strategies for 135 patient care surge capacity Use of telemedicine technologies in the 137 management of infectious diseases: A review Home testing pilot launched in london to cut hospital visits and 139 ambulance use