Fast and accurate detection of coronavirus infection in the human body caused by the severe acute respiratory syndrome coronavirus-2 (SARS-COV-2) variant helps us better monitor and control this pandemic disease spread worldwide. In this work, we created and numerically investigated a highly sensitive portable PCF biosensor. The guiding properties are evaluated by the finite element method (FEM). In contrast, the good sensing properties of this sensor are estimated by the following: confinement loss intensity, high wavelength sensitivity, large FOM, large amplitude sensitivity depth, maximum wavelength resolution, and significant LOD. The receptor-binding-domain (RBD) protein of the virus spike, RNA protein of the mutated virus, single-stranded, and immunoglobulin (IgG) protein presented in human antibodies are used as target analyte solutions. In contrast, sterile phosphate-buffered saline (PBS) is used as a solute. The sensing properties of the sensor vary with the variation of the refractive index (RI). Following the severity of COVID infection, the corresponding RI of the target analyte varies between 1.3348 and 1.3576 for the RNA protein concentrations of SARS-COV-2, 1.3348 and 1.3468 for virus spike RBD protein concentrations, and 1.3348 and 1.3465 for human monoclonal antibodies (mAbs) of IgG protein concentrations. The critical study is demonstrated for the RI ranges from 1.3348 to 1.3576 for our proposed sensor. The average wavelength sensitivity value of $1.68\times 104$ nm/RIU is found for spike RNA protein detection, and $1.465\times 104$ nm/RIU is estimated for SARS-COV-2 spike protein detection. The maximum FOM of 67.50 RIU$-1$ and 66.67 RIU$-1$ are exhibited, respectively, for the RNA protein and viral spike protein detection. For the IgG protein quantification, the average wavelength sensitivity, maximum FOM, and minimum value of LOD of this sensor are estimated to be $1.10\times 104$ nm/RIU, 56.90 RIU$-1$, and $5.36\times 10-8$ RIU$2$/nm, respectively. The significantly minimal LOD of $1.46\times 10-11$ RIU$2$/nm and maximum sensor resolution of $2.34\times 10-7$ RIU are found in spike RBD detection. The median values of the amplitude sensitivities of this sensor were estimated at around 151 RIU$-1$, 121 RIU$-1$, and 124 RIU$-1$ for virus RNA detection, virus spike protein detection, and human antibody IgG protein detection. Owing to high sensitivity and fast processing time, this sensor will be applied to point of care (PoC), resource-limited medical diagnosis, and vaccinology.