## 3 Non-Invasive Clinical and Physiological Presentations (CPPs) of COVID-19  
The impact of diseases, such as cancers, often involves clinical diagnoses that require invasive procedures such as biopsies and pathological tests. In contrast, non-invasive approaches are preferred by patients as they allow medical procedures to be conducted more comfortably, avoiding the inconvenience and pain associated with invasive procedures. However, these technology-based methods must receive approval from government and regulatory agencies, such as the Food and Drug Administration (FDA), before complete autonomous usage is permitted. Once approved, these methods can be easily scaled up for public utilization, alleviating the burden on overwhelmed healthcare systems, as experienced by many countries during pandemics [18]. This article introduces a novel approach for monitoring COVID-19 symptoms on a public health scale using the mPOC mechanism, which is based on the bidirectional mHealth Disaster Recovery System (mDRS) [5]. The mPOC system relies on the physiological symptoms and clinical presentations, which include fever, dry cough, sore throat, fatigue, and shortness of breath, which can be seen in severe cases and in elderly patients. The gastrointestinal symptoms (vomiting and diarrhea), cardiac presentations (myocarditis, pericarditis and/or atrial fibrillation), and loss/reduction of senses (smell and taste) are less commonly observed in recent COVID-19 subvariants (e.g., XBB) [19; 20]. By utilizing these clinical and physiological presentations (CPPs) within its algorithm, the mPOC system assesses the user's health condition and calculates two crucial indices: the Predictive Exposure Index (PEI) and the Deterioration Risk Index (DRI). These indices trigger appropriate warnings to the user and facilitate the transmission of updates to and from the Outbreak Tracking Center (OTC). The selection and weighting of CPPs are determined by their non-invasive detectability, prevalence, specificity, sensitivity (accuracy), and demographic-specific considerations, enabling the system to adapt to individual users. Before delving into the list of CPPs, it is important to define several terminologies associated with the characteristics of CPPs:  
Prevalence (PR): Percentage of diagnosed (or to be diagnosed) people displaying the physiological presentation. Timeline: The entire timeline of the disease can be divided into several segments:  
Incubation Period (IP)--The period right after the initial exposure to the virus until the time that the initial symptoms appear, which can take up to 5 days for XBB Omicron subvariant (XBB 1.15 and 1.16) [19]. Early Stage (ES)--The duration of the initial signs and symptoms of Omicron subvariants, which can take anywhere from 1 to 5 days, with an average of 3.63 days (95%CI: 3.25-4.02 days). During this stage the patient exhibits flu-like symptoms [21]. Advanced Stage (AS)--This is when the disease progresses into a more serious stage and the patient's overall health starts to decline more rapidly. This could happen between 5 to 7 days after the initial exposure. The final stage follows the AS, which can either lead to the Recovery Stage (RS), when the patient starts to feel better and recovers from the disease (at least 3 days after last main CPPs), or it progresses into a Terminal Stage (TS), when the patient enters a critical phase, often requiring a ventilator or a breathing tube. After TS, the patient either survives and enters the RS or passes away. Specificity and Sensitivity (SS): Is the percentage of accuracy of diagnosis based on the detection of a specific CPP. Overall, diagnosing COVID-19 is linked to a relatively low sensitivity and a high specificity, meaning the initial home-based tests (RAT: Rapid Antigen Test) may initially yield negative results while the patient has COVID-19 and, eventually after a few tests, the result will turn positive. However, if the test result becomes positive, it is with a high percentage (over 95%) of certainty that the patient is actually COVID positive.