Primary care-based health surveillance actions in response to the COVID-19 pandemic: contributions to the debate

We conducted an integrated literature review aimed at reflecting on the challenges related to primary care-based health surveillance actions in response to the COVID-19 pandemic in selected countries. The study included countries with different PHC models that adopted surveillance as an approach to control the transmission of COVID-19. We performed a search in October 2020 for relevant literature and norms and guidelines related to the organization of primary health care (PHC) in response to the pandemic on official government websites and the databases Web of Science and Science Direct. The integrated health surveillance actions demonstrated that efforts were more focused on risks, with some countries adopting innovative and effective measures to respond to COVID-19, considering emerging needs within PHC. However, in addition to ethical controversies and operational difficulties, access to technology was a challenge in actions developed by some countries due to social inequalities.


Introduction
Since the World Health Organization (WHO) declared the COVID-19 outbreak a pandemic on 11 March 2020, serious concerns have been raised about the effects of the coronavirus (SARS-CoV-2) on global health, society and the economy, particularly among vulnerable populations in low and middle-income countries with fragile health systems 1,2 .
As with previous outbreaks and pandemics, the control of the COVID-19 pandemic depends on the early detection of cases and contacts, followed by isolation measures and quarantine to interrupt community transmission and mitigate the health impacts of the coronavirus 3 .
Globally, countries have adopted a variety of strategies to tackle and control the COVID-19 pandemic -such as community-based testing, contact tracing, isolation and other social and public health measures -which are crucial to slowing down transmission and reducing mortality 4 .Within this context, a robust health surveillance system is essential to control spread and guide the ongoing implementation of prevention measures.
A critical element of public health systems, health surveillance includes the collection, analysis, interpretation and systematic and continuous dissemination of data that is essential to the planning and implementation of interventions 5 .Other authors suggest that health surveillance is essential for providing information and guiding both individual diagnosis and treatment (clinical approach) and interventions targeting specific population groups addressing the social determinants of health 6,7 .Health surveillance is mediated by the traditional generation of surveillance data or by the interpretation of data from surveillance systems, adapted and used by the various levels of the health system to meet the needs and cultural and population dynamics of each country 5 .
Considered the main point of entry of the health system, primary health care (PHC) is the foundation for direct surveillance with a timely response and outbreak management.With the intensification of the pandemic, the initial failure to detect and trace contacts and the consequent safe relaxation of social isolation, coordination between public health surveillance and PHC has become critical to guaranteeing technical, operational and logistical support and providing the necessary resources to develop and implement a new modus operandi, facilitating greater public participation and optimizing the use of the social facilities necessary for the effective containment of the spread of COVID-19 8 .
A variety of approaches used in different disease outbreaks support the integration of health surveillance at the primary care level with wider responses at regional level 9 .These approaches involve the use of data aggregation systems, data dashboards and digital epidemiological surveillance.These data sources are increasingly being integrated into the formal surveillance landscape and play a role in COVID-19 surveillance 10,11 .Such monitoring initiatives are part of a set of actions designed to address the social determinants of health and health risks in a given population and region, ensuring the comprehensiveness of health care, which includes both individual and collective approaches [12][13][14] .
In view of the above, this article aims to identify and reflect upon the experiences and limitations of health surveillance actions integrated with primary care developed in response to COVID-19 in the health systems of selected countries.

methodology
We conducted an integrative literature review to compile experiences related to primary care-based health surveillance in response to COVID-19 in a selection of countries affected by the pandemic.
Given the countless challenges of undertaking comparative studies in the field of health policy, the risk of semantic confusion, superficiality, mistaken descriptions, caricatures, rhetorical distortion and unwarranted inferences is great 15 .
Despite the similarities and differences between the actions developed by different countries, the objective of this study was not to compare the different approaches adopted and replicate them in Brazil, but rather to develop a synthesis of international experiences of integrated surveillance actions in the response to COVID-19.In this respect, we depart from the assumption that a critical comparative analysis of the responses adopted by different health systems requires a more in-depth understanding of the context in which they were produced 16 .
The study includes experiences from South Africa, Argentina, Australia, China, South Korea, Cuba, the United States, France, Italy, India, Singapore and the United Kingdom.Despite having different PHC models, the selected countries adopted an active surveillance approach (inten-sive and extensive) to control the transmission of COVID-19.Surveillance is directed at both asymptomatic and symptomatic people with the support of PHC professionals and the community and referral flow coordinated with other emergency and hospital services.Except for the United States, whose care and public health surveillance models are fragmented and differ from state to state, meaning that the federal government has a low regulatory and coordination capacity (Chart 1).
The integration of PHC with other levels of care is an essential feature of a wider-reaching PHC approach, the concept adopted here.In addition to integration within the health system, intersectoral coordination is another crucial element of effective PHC.
We performed a search of the Web of Science and Science Direct databases for publications on the COVID-19 response in PHC, using a combination of the following descriptors: Health Primary Care AND Public Health Surveillance AND Coronavirus Infections.The data were collected in October 2020.
Articles written in Portuguese, English and Spanish were read in the original language.Those written in Chinese and French were translated using Google Translate.After the search, selection and reading of the full-text version of the articles, the publications were synthesized as follows: author and year of publication, country of origin, title and health surveillance actions (Chart 2).

health surveillance actions
Public health emergencies have a major impact on local populations and health surveillance systems.The adoption of multiple surveillance mechanisms helps ensure broader coverage, since every lost case can lead to chains of transmission that may be difficult to contain afterwards.
Countries vary widely in their capacity to prevent, detect and respond to outbreaks and in relation to the capacity for government response and degree of local autonomy and responsibility for health surveillance.Generally speaking, the actions consist of active and passive public health surveillance, with some variations, or a mixture of the two approaches, depending on the possible technological arrangements within the organization of practices 16,17 .
With regard to surveillance approaches, active surveillance consists of regular monitoring to obtain information on population health status and behavioral risk factors.It is performed by health professionals with or without the participation of the community and with the support of Information Technologies and Health Care and communications channels 18 .Passive surveillance is a system in which health authorities examine reports provided by hospitals, clinics, public health facilities and other sources, stories, rumors and other data on health events using strategies based on sentinel health centers, aggregation methods or digital surveillance and through contact tracing 19,20 and passive monitoring of social media data to measure disease activity (Figure 1).
In China, the initial epicenter of the pandemic, active surveillance measures were implemented.With the support of local committees, PHC doctors played an active role in health education, the mobilization of residents and volunteers, and monitoring confirmed cases (daily monitoring of health status and psychological support for individuals in quarantine) 21 .Passive surveillance approaches were also used, using digital surveillance to provide online prescriptions, instant messaging and electronic dashboards to disseminate information and maintain contact with specialist outpatient centers 22 .
Networks led by PHC doctors made a significant contribution to data collection and epidemiological research, through health screening committees, contact tracing and investigation of infection sources, as well as the use of social media apps to generate a combination of aggregated health data and personal risk of infection classification [23][24][25] .Other actions included surveillance of people who had been in contact with wildlife and behavioral risk factors (certain eating habits, such as eating bats) 26 .
Singapore prioritized passive surveillance through the implementation of an enhanced surveillance system and contact tracing, identifying and reporting the location of people in quarantine using a global positioning system (GPS).This information was linked to the results of serological testing, permitting the creation a map of the chain of transmission and sharing of information on infectious diseases from previous experiences of respiratory outbreaks between epidemiology services 27 .
In South Korea, all PHC services carry out active screening in households and passive screening by telescreening 28 .People who tested positive were referred to health centers for face-to-face appointments, testing and diagnosis.Confirmed, probable and suspected cases were then monitored on a daily basis through the application of individual risk assessments by PHC doctors to Chart 1.General characteristics of the health systems and organization of PHC in the selected countries.Chart 1.General characteristics of the health systems and organization of PHC in the selected countries.

Country
In the US, health surveillance was developed by Centers for Disease Control and Prevention (CDC) and the Department of Defense Global Emerging Infections Surveillance and Response System (DoD-GEIS).The following systems were used: ILINet, a national surveillance system for influenza-like illnesses, the databases ProMed and Epi-X, and reports derived from the Outbreaks Near Me app.However, while informative, these systems can result in selection bias, excessive interpretation of results due to lack of integration with official surveillance resulting from the fragmentation of the health system and PHC, and variations in decision-making by state health managers 30 .
Italy opted for passive surveillance, using integrated COVID-19 surveillance data 31 collected by the Instituto Superiore di Sanità (ISS) via an exclusive online platform, electronic questionnaires and daily infographics processed exclusively for the purposes of epidemiological and microbiological surveillance in the context of the COVID-19 pandemic.The data permit the government to monitor the epidemiological situation at national and regional level 31,32 .
The interprofessional health teams in Medicare Locals in Australia prioritize contact tracing and vulnerable groups -especially the elderlyand monitoring people with mild respiratory disease symptoms (syndromic surveillance) in the

South
community 35 .At national level, data is provided by the internet-based FluTracking syndromic surveillance system, the Australian Sentinel Practices Research Network (ASPREN), Victoria Sentinel Practice Influenza Network (VicSPIN), general practice (GP) sentinel surveillance systems, and the Commonwealth GP Respiratory Clinics 34 .Surveillance includes the aboriginal population and Torres Strait islanders 35 .South Africa chose active community-based surveillance to promote early detection and rapid confirmation through contact tracing, setting up quarantine centers and care support under the Integrated Disease Surveillance and Response framework (IDSR), which provides a framework for syndromic surveillance and entry point for identifying, characterizing and responding to community transmission of COVID-19 36 .In addition, the Africa Health Research Institute (AHRI) implemented demographic surveillance systems for community surveillance in rural areas.These systems are a vital tool in the COVID-19 response in remote areas, permitting screening of symptoms in household members [37][38] .
With limited resources and a not so robust health system, India uses a participatory surveillance system called Aarogya Setu ("bridge to health" in Sanskrit) to prevent spread and control the pandemic 39 .This system complements the India Integrated Disease Surveillance Program using Bluetooth and telephone data to identify the proximity of infected people, comparing databases of confirmed cases to classify individual risk status (low, medium and high) 40 .Individuals are advised of the measures that should be taken based on risk assessments and test counselling and informed the location of the nearest test center.The application also has a chatbot, which provides constant updates from the Ministry of Health and state help line numbers 40,41 .
In France, the use of a sentinel network by PHC doctors was supported by the installation of java-coded applications on health center com- puters.The app allows the reporting of cases, implementation of surveillance protocols and questionnaires and case description in areas with poor internet access, since the computers are linked to a central server in national surveillance centers 43.In the United Kingdom, the National Health Service and Public Health England implement a community-based surveillance system integrated with various national syndromic surveillance systems coordinated by the Real-Time Syndromic Surveillance Team (ReSST).The Oxford Royal College of General Practitioners (RCGP) Research and Surveillance Centre (RSC) provides weekly surveillance data reports 11 .The web-based syndromic surveillance system uses daily search query frequency statistics obtained from the Google Health Trends API focusing on queries about COVID-19 symptoms and monitoring models 43 based on previously established Influenza internet search algorithms (FluSurvey) currently included in Public Health England's weekly COVID-19 reports 44,45 .This allows for the analysis of anonymous health data from various sources and facilitates the search for trends that indicate above normal disease levels.Bulletins are published to keep public health professionals up to date, aggregating symptom data in outpatient settings 44,45 .
Argentina's Ministry of Health implemented a contact tracing plan called Detectar in areas in which an increase in the number of cases has been detected or estimated.Launched in May after a sharp rise in the number of cases among lower-income families in densely populated neighborhoods in Greater Buenos Aires, the plan was subsequently expanded to the rest of the country [46][47][48] .
In Cuba, the country's previous experience with the dengue and Zika epidemics proved to be an advantage.The country already had a national diagnosis and surveillance network, supported by Provincial Hygiene, Epidemiology and Microbiology Centers, a national network of WHO-compliant diagnostic laboratories and a national reference center lab for infectious diseases at Havana's Pedro Kourí Tropical Medicine Institute de Havana 49,50 .Before the appearance of the first case, the Ministry of Health had trained its health professionals in disease management and community-based surveillance 49,50 .
Following protocols, PHC teams conduct continuous community health assessments (public health and epidemiological situation) and individual and family health assessments to detect respiratory symptoms.Daily screening of suspected and confirmed cases was performed in every neighborhood with the participation of approximately 28,000 volunteer medical students 49,50 .Home visits were used to broaden the monitoring of high-risk people and confirmed cases in home isolation, conducting physical examinations and comprehensive assessments with emphasis on vulnerable groups 50,51 .
A little-used method of surveillance was the detection of SARS-CoV-2 in longitudinal samples of metropolitan waste water collected during the early stages of the pandemic in countries like Spain and France, enabling the detection of viral RNA, which is related to the increase in number of declared cases 43 .The routine analysis of waste water is a sensitive and cost-effective COVID-19 surveillance technique, resulting in a significant improvement in preparedness in the event of future or reoccurring viral outbreaks 53 .

Challenges, limitations and final considerations
Public health surveillance is essential for understanding the epidemiology of diseases and provides a solid foundation for the implementation of control measures.The majority of countries included in this study adopted different approaches to public health surveillance, ranging from the systematic recording of common medical conditions using administrative data systems, vital statistics and annual health surveys.However, the scope of public health surveillance actions may be limited, even in countries with universal health systems, due to the poor quality of surveillance and public health response, for example as a result of the decentralization of actions to districts or provinces, which can lead to a loss of locally collected data 53 .
Despite having systems considered to be effective for detecting major public health problems, the countries that adopted sentinel systems, such as France, the United Kingdom and US (with private PHC), showed a low level of sensitivity to rare events such as the early emergence of a new disease.This is because these infections can emerge in any part of the population and require large-scale monitoring integrated across all levels of care.
Another interpretive challenges observed in this article is the comparison of ways of life and territorial occupation in different countries and their respective care models.Even with robust surveillance systems, hospital-centric care mod-els in high-income countries may be less effective for vulnerable groups living in densely populated areas, especially when social distancing is not maintained.Hospital-centric systems tend to be less effective for vulnerable populations in lower and middle-income countries, regardless of the type of surveillance and/or degree of integration with PHC.
In contrast, PHC models strongly oriented towards the community tend to achieve more effective surveillance outcomes as they promote actions drawing upon cultural competence implemented in social spaces by interprofessional teams, often including community workers.In this regard, the integration of surveillance and PHC catalyzes the performance of the entire health system, minimizing the adverse effects of the pandemic, even in areas with limited social protection.
Over the last two decades, other approaches have been used to address the gap between PHC and health surveillance, such as the use of data from online news sites, news aggregation services, social media and web searches by countries like Australia, South Korea and Singapore, and longitudinal community-based cohorts in India and the United Kingdom 54 .Digital surveillance uses technologies to support active and passive epidemiological intelligence using digital platforms to aggregate datasets that enable the identification of cases and groups of infections, rapid tracing of contacts, monitoring of travel patterns during lockdowns and public health messaging to wide audiences 55,56 .
It is important to highlight that the widespread use of digital surveillance raises some concerns, including the violation of privacy both during and after the outbreak, as not all digital interventions were consensual or explicitly mentioned the consent option for the use of data for specific ends and a given period of time 57 .
One example of the above is the use of smartphone apps by South Korea to report the movement of people with COVID-19, raising fears that this initiative could lead people to avoid testing (or other measures imposed by the government) so as not to suffer a violation of their privacy 25 .One of the weaknesses of contact tracing apps is that a large part of the population need to use them and follow the guidance for them to effectively interrupt community transmission 58 .Practical questions also remain, such as which contacts are considered close enough for transmission and when the exposure time is considered long enough to trigger an alert.
Digital surveillance can therefore generate a sense of being controlled and be seen as an obstacle to autonomy, having negative effects on motivation and well-being 59 .Infrared sensors, including the use of thermal imaging cameras to identify possible cases by detecting fever (for example in airports), may generate a false sense of control over the situation.Another obvious concern is the large number of false positive and false negative results, meaning that monitoring strategies are unlikely to have a substantial effect other than raising awareness 60 .
Data dashboards have been used extensively during the pandemic, collecting public health data (including confirmed cases, deaths and number of tests) in real time to keep the public informed and helping policy-makers refine interventions.COVID-19 dashboards 61 normally focus on time series graphs and geographical maps, ranging from regional statistics to case-level coordinate data.Few dashboards include an analysis of contact tracing or community surveillance data 62 .
Mathematical models have been widely used to estimate spread and other COVID-19 health outcomes, as well as disease burden.Such models require knowledge of the main transmission parameters, such as the serial interval (SI) and the interval between onset of symptoms in the infecting and infected person in the chain of transmission [63][64][65] , to enable the estimation of the interval between infection of primary and secondary cases and time-varying reproduction numbers (how many secondary cases are caused by a typical primary case during the infectious period) during the course of the pandemic 59,66,67 .
The quality and consistency of data remains a concern.The lack of official standards and inconsistencies in government statistics between countries make global comparisons difficult 12 , especially in countries with striking regional differences, such as Brazil, France and Canada.In addition, up-to-date and accurate offline government statistics are not always evenly accessible.
In China, current policies and technology systems have marked limitations, preventing the integration of clinical care and PHC and collaboration between PHC and other levels of care (for example, hospitals), and make it difficult to ensure a sufficient number of properly trained and an adequately paid PHC professionals 68 .
The literature also shows that surveillance services should not operate in isolation and need to be integrated into existing public health systems.Although innovative digital technologies and data sharing enhance the effectiveness of control measures, they have a number of limitations in relation to the COVID-19 response.This is because they are vertical interventions based on traditional case reporting, recording and investigation and syndromic surveillance practices, meaning PHC actions -which account for 80% of all mild cases -remain disjointed.In contrast, comprehensive multi-sectoral health surveillance integrated with PHC has shown itself to be effective and capable of ensuring continuous monitoring of the range of health problems affecting the local population, both during and after the pandemic.A surveillance system integrated with PHC contributes to the control of transmission in the community, orienting the implementation of mitigation measures towards the community, taking into account scale, time and duration and promoting strategies tailored to local demands.
In this respect, participatory disease surveillance has also shown itself to be an effective strategy for monitoring communicable diseases, in which citizens are actively involved in self-reporting symptoms or events in order to help public health experts to aggregate and analyze data to inform public health interventions 69 .However, biased results may arise in primary care surveillance systems based on voluntary participation due to the lack of representativeness of the monitored population and uncertainty about population denominators.
The Cuban experience reveals a common element for the organization and professional integration of PHC into the surveillance system and broader analysis of health problems, focusing not only on the systematization of general indicators, but aimed at informing the planning and organization of systems and services.This requires a PHC model that seeks to understand local living and working conditions and the forms of organization and operation of local government and non-governmental organizations.In other words, a care model articulated with representative collective decision-making spaces within society and tailored to different realities in order to provide comprehensive and equitable care 51,70,71 .
The primary care-based surveillance model should include the following: the articulation of interprofessional team practices, including primary care providers; a health surveillance, health promotion and disease prevention funding system or incentive program; information technology systems to promote the continuous and systematic collection of data and implementation of common plans and protocols; and the capacity to detect and report new and emerging diseases using platforms integrated across local, provincial, national and international health systems.
Finally, the experiences analyzed by this study demonstrate that, although robust surveillance systems are essential tools for detecting and monitoring outbreaks and public health emergencies, strong primary care systems form the foundation for any response to health emergencies.

Chart 2 .
Types of surveillance actions and data collection methods adopted by the selected countries in their COVID-19 responses.

figure 1 .
figure 1. Integrated surveillance actions in the context of a public health emergency.Source: Authors' elaboration.

type of health system PhC model Organization of PhC teams Primary care response to the COVID-19 pandemic
General characteristics of the health systems and organization of PHC in the selected countries.
29 continues determine the severity of the disease and the necessary parameters for quarantine and isolation.PHC appointments were integrated with health surveillance and provided an estimation of the local and national epidemiological situation of COVID-1929.Source: Authors' elaboration.