Question

Compare the stages of disease (phases of infection and disease) to microbial growth curve, use annotated diagrams/cartoon as appropriate in your interpretation/illustration

Answer 1

Answer:

Any infection setting in after exposure to the causative agent normally passes through the following stages:

1. Incubation period - This is the period when the victim has been exposed to the causative agent , microbe or any of its products which will harm the person as time progresses. In this period the patient even though harboring the pathogen , does not show any signs and symptoms of disease as the number of pathogens has not crossed the infectious dose.
2. Prodromal period -In this period, the early signs of disease and few symptoms start manifesting as the organism has taken foothold and has reached the organ of its' choice. As the signs manifest the immune system also starts responding to the corresponding infection.
3. Illness - This is the acute phase of infection when organism has reached its maximum peak and has started harming the host. All the signs and symptoms are easily visible and the host immunity system is fully activated and responding in all possibility.
4. Recovery period - In this final phase of infection, the host has overcome the invader and has started recovering from the illness. The symptoms are on decline and so is the causative agent. The  patient starts feeling better by virtue of correct treatment and immune system has removed the pathogen and stored memory of the pathogen to be ready if and when the next attack comes.

The corresponding 4 phases of the microbial growth curve are :

1. Lag phase - In this phase the organism has just entered the host by use of its virulence factors or by breach of host defenses. The microbe has just started to multiply.
2. Log phase - This is the phase where organism has got the foothold and has entered the exponential growth phase of its life. There is uncontrolled multiplication and the number of pathogen shoots up considerably in a short amount of time.
3. Stationary phase - The microbe has reached its peak and the illness has manifested completely in the host. In this phase multiplication continues at slower rate and death has started for the microbe. It is also the most infectious phase as microbe has gained access to exit portals for its spread to new hosts.
4. Decline or Death phase - In this phase, the rate of death of microbe is much higher than its multiplication rate resulting in fall in number of microbes and recovery for the patient. The fall in numbers is automatic in self limiting diseases whereas it is induced by treatment wherever necessary.