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Virology (MD PhD) (Subject) / Regoes (Lesson)
- R0 = the basic reproduction number - Number of secondary infected hosts when one primary infected host is placed into a wholly susceptible population Growth rate of infected is larger 0, if βS/(a + r) > 1--> virus spreads! (doesn't say anything about how fast) B(S,I,R) : birth rate of susceptibles δ : natural death rate β : infectivity (per contact between S and I) a : natural + disease induced death rate r : recovery rate q : rate of loss of immunity
- age at infection = life-span/R0 if - immunity is life-long (q = 0)- case fatality small (δ, a << r )
- herd immunity achieved if the fraction of completely immune hosts is pc = 1/(1/R0) pc = critical vaccination coverage
- Basic model of virus dynamics target cells: dT/dt = lambda - dT - bVT infected cells : dI /dt = bVT aI freevirus: dV/dt = kI uV lambda: rate at which new target cells are generatedd: death rate of target cellsb: infectivity of virus (per contact with target cell)a: death rate of infected cellk: shedding rate of virus from infected cellc: clearance rate of virus
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