**1. Introduction**

The coronavirus disease caused by the SARS-CoV-2 virus (COVID-19) pandemic induced overload in acute healthcare and significantly increased the burden of chronic diseases. One of the new manifestations of chronic diseases is the post-COVID-19 disorder, for which a common definition has not yet been established, but which creates the preconditions for expanding the prevalence of related diseases. The results of an online survey of 3762 participants with confirmed (diagnostic/antibody

positive; 1020) or suspected (diagnostic/antibody negative or untested; 2742) COVID-19, performed in 56 countries, from September 6, 2020 to November 25, 2020, demonstrated that 1700 respondents (45.2%) required a reduced work schedule compared to pre-illness, and an additional 839 (22.3%) were not working at the time of survey due to illness. After 6 months of the post-COVID conditions, the most frequent symptoms were fatigue, post-exertional malaise, and cognitive dysfunction. Cognitive dysfunction or memory issues were common across all age groups (~88%) [1]. Already in July 2020, Dr. Anthony Fauci, the Director of the National Institute for Allergy and Infectious Diseases (US Department of Health and Human Services), assumed that patients post-COVID-19 can develop "a post-viral syndrome that's very strikingly similar to myalgic encephalomyelitis/chronic fatigue syndrome" [2].

The authors, in one of the previous studies on the COVID-19 pandemic consistencies in healthcare [3], revealed that since October 2020, several articles have reported myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) as a potentially post-COVID-19-associated disease [4–11]. The literature reviews on the potential causal interaction between post-COVID-19 and ME/CFS also appeared in the following period [12–19]. The reviews' results highlighted problems associated with the definitions and diagnostic criteria for ME/CFS and post-COVID-19 disorder. There were various manifestations of the interaction between post-COVID-19 and ME/CFS, from the similarity of the symptoms to the assumption that it is the same disease [3]. Over time, the COVID-19 long-haulers reported an overall reduction of most symptoms including unrefreshing sleep and post-exertional malaise, but an intensification of neurocognitive symptoms. When compared to ME/CFS, the COVID-19 sample was initially more symptomatic for the immune and orthostatic domains but over time, the long-haulers evidenced significantly less severe symptoms than those with ME/CFS, except in the orthostatic domain [20]. However, almost all publications indicated the need for further research into the similarities and differences between post-COVID-19 and ME/CFS to determine the nature of these conditions and define risk factors, prevalence, and possible interventions [3].

Concerning the definitions, ME/CFS commonly is defined as a poorly understood, serious, complex, multisystem disorder, characterized by symptoms lasting at least 6 months, with severe incapacitating fatigue not alleviated by rest, and other symptoms—many autonomic or cognitive in nature—including profound fatigue, cognitive dysfunction, sleep disturbances, muscle pain, and post-exertional malaise, which lead to substantial reductions in the functional activity and quality of life [21]. The common definition of post-COVID-19 disorder has not yet been established, but the results of some studies suggest, for instance, that it is composed of heterogeneous sequelae that often affect multiple organ systems, with significant impacts on morbidity, mortality, and quality of life [1]. Regarding the defining post-COVID-19 symptoms, based on the relapsing/remitting nature of post-COVID-19 symptoms, the following integrative classification was proposed by researchers: potentially infection-related symptoms (up to 4–5 weeks), acute post-COVID-19 symptoms (from week 5 to week 12), long post-COVID-19 symptoms (from week 12 to week 24), and persistent post-COVID-19 symptoms (lasting more than 24 weeks) [22]. Therefore, in the context of the time reference, ME/CFS is most closely associated with persistent post-COVID symptoms.

Persistent post-COVID symptoms were considered in light of a new "syndrome," as the British Medical Association defines a syndrome "as a set of medical signs and symptoms which are correlated with each other and associated with a particular disease" [22]. Accordingly, the term "Persistent Post-COVID-19 Syndrome (PPCS)" *The Advantages of an Integrative Approach in the Primary Healthcare of Post-COVID-19… DOI: http://dx.doi.org/10.5772/intechopen.106013*

was introduced in practice, as a pathologic entity, which involves persistent physical, medical, and cognitive sequelae following COVID-19, including persistent immunosuppression as well as pulmonary, cardiac, and vascular fibrosis [23]. Consequently, some authors note that the preliminary findings raise concern regarding a possible future ME/CFS-like pandemic in SARS-CoV-2 survivors [24].

The prevalence of ME/CFS in population varies from 0.19% to 7,6% [21]. Based on the earlier studies on other infections, researchers suggested that 10% of COVID-19 survivors could develop ME/CFS [2]. Accordingly, it is estimated that the US ME/CFS prevalence of 1.5 million prior to the COVID-19 pandemic (and an annual economic impact of \$36–51 billion) could rise to between five and nine million people. This would incur an annual US economic impact of \$149 to \$362 billion in medical expenses and lost income, exclusive of other costs, such as disability benefits, social services, and lost wages of caretakers [25].

Considering the health-related quality of life (HRQoL) ME/CFS demonstrates a significant negative impact on general health, physical functioning, emotional health, vitality, cognitive health, and well-being, in different populations [12, 26–32]. Various tools are used to elaborate the HRQoL, such as EuroQoL-5 Dimensions (EQ-5D-3L) [26, 31] and (EQ-5D-5L) [12], 36-Item Health Survey (SF-36) [29, 31], Pediatric Quality of Life Inventory (PedsQL) [28], overall health status reported on a Visual Analogue Scale (VAS) [12, 27, 30], Abbreviated World Health Organization Quality of Life questionnaire (WHOQOL-BREF) [32], completed by people with ME/CFS, and Family Reported Outcome Measure (FROM-16) questionnaire [30, 32], completed by family members. Simultaneously, HRQol widely affected by all post-COVID-19 domains [24] mostly is assessed by EuroQoL-5 Dimension EQ-5D-5L and VAS [33–35].

The predominant score of ME/CFS and PPCS patients' healthcare is related to primary healthcare, given that patients of these syndromes are mostly treated on an outpatient basis [36–39]. The unifying issues for these diseases are also complex and multisystem nature, which requires coordinated integrative multidisciplinary teamwork to achieve treatment goals [34, 39]. Previous research demonstrated significant results of the interdisciplinary approach, such as the "Recovering from COVID" course, which took a whole system, biopsychosocial approach to understanding COVID-19 and post-viral fatigue and was led by an interdisciplinary team consisting of a clinical psychologist, physiotherapist, occupational therapist, dietitian, speech and language therapist, and a personal support navigator [34].

Moreover, COVID-19 is associated with high rates of psychiatric symptoms, including anxiety, depression, fatigue, sleep disruption, and posttraumatic stress, and consistent risk factors for psychiatric symptoms include the history of a psychiatric disorder and female gender [40]. Researchers notified that while the exact etiology remains unknown, and future research is needed, it is now recognized that overlapping symptomology between post-COVID-19 syndrome and ME/CFS provides a promising avenue for the development of post-COVID-19 rehabilitation [34].

Prior to the COVID-19 pandemic, it was assumed that primary care transformation will usher in a new era of advanced team-based care with extensive roles beyond the physician to build authentic healing relationships with patients [41]. The pandemic hampered the development of primary healthcare, with an emphasis on the hospital sector, but some achievements remain topical. In the context of integrity, the integrative and patient-centric view argues strongly that populations with physical,

developmental, or cognitive disabilities—often with related chronic conditions or complex illnesses—endow the concept of healthcare integration with unique logic and meaning. Vulnerable individuals have complicated and ongoing needs (which frequently are part-medical, part-physical, part-psychological, and part-social), experience difficulties in everyday living, require a mix of services delivered sequentially or simultaneously by multiple providers, and receive both cure and care in the home, community, and institutional settings [42]. These statements mostly are applicable also for ME/CFS and post-COVID-19 conditions.

In order to organize person-centered health services for a growing number of people with multiple complex health and social care needs, a shift from fragmented to integrated health services delivery has to take place. For the organization of governance in integrated health services, it is important to better understand the underlying factors that drive collaboration, decision-making, and behavior between individuals and organizations [43]. There are multiple levels of integrated care, and four levels of health services delivery are investigated more often: the personal, the professional, the management, and the system level [43, 44]. In addition to the different levels, researchers present two crucial dimensions of integration: systemic integration, which includes the coherence of rules and policies in the health system, and normative integration, which comprises the role of shared values in coordination and collaboration [43–45].

In the scope of this research, the authors focus on two central levels of the integrative model—the personal level, assuming the relation with the person-centered approach, and the professional level of collaboration (**Figure 1**).

#### **Figure 1.**

*The research focused on the personal and the professional level of integrated health services for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and post-COVID-19 patients.*

The following section provides an example of professional collaboration and patient outcomes in the integrative approach for ME/CFS and post-COVID-19 care. *The Advantages of an Integrative Approach in the Primary Healthcare of Post-COVID-19… DOI: http://dx.doi.org/10.5772/intechopen.106013*
