abstract virus background. pathogen affecting the respiratory tract. covid-19 infection. concept of pandemic, viral

2019ncov allergy background bacterium biology blood body cancer cell cold concept contagion contagious covid19 drug epidemic epidemiology fever flu fungi giene h1n1 health hepatitis hiv humanhy ill illness immune medical medicine microbebacteria microbiology microscopic molecules ncov organism outbreak pandemic research retrovirus science scientific sickness vaccine viral virology virus