Natural History of Covid-19

Natural history refers to the progress of a disease process in an individual without intervention over time including complications, symptoms change, remissions, disability, cure , recovery and death.

The process begins with exposure to or accumulation of factors capable of causing disease in a susceptible host.

Most diseases have a characteristic natural history although the time frame and the specific manifestations of the disease vary from person to person.

Incubation Period of Covid-19 : (Colonization)

• Pathogen has embedded in the body of a susceptible host.
• No signs and symptoms are apparent
• Micro- organisms have invaded the host and are migrating to various tissues causing some pathological changes.
• the pathogens have not increased to sufficient numbers to produce enough toxins to produce discomfort nor cause the individual to be infective.
• the period is usually variable in length and usually disease specific.

Podromal stage

• first symptoms of the disease appear
• patient is aware of discomfort but no precise signs/symptoms to permit diagnosis.
• patient highly contagious to others including nosocomial.
• host immune responses become operative.
• marks transition from sub – clinical to clinical disease.

Clinical stage: (Isolation or cohorting in a absence of co-morbidity)

• period illness
• characteristic disease symptoms occur e.g coughing,headache,fatigue,flue fever and chill characterized by high temperature.
• most diagnoses are made during this stage.
• during the acute stage of this period, the patient is sufficiently ill to alter work/school activities.
• in some people the disease process may never progress to clinically apparent illness.
• in others the disease process may result in a wide spectrum of clinical illness, ranging from mild to severe or fatal symptoms like respiratory complications including shortness of breath.
• chemotherapeutic intervention or adequate immune response may lead to recovery.

Decline stage

• period of decline if disease is not fatal
• first sign of recovery manifests i.e disappearance of signs and symptoms.
• disease starts to end.
• disease becomes latent or intermittently recurs.

 Convalescent stage

• disease ends.
• progresses to carrier stage (colonization ) or freedom from pathogen.
• body’s defense may acquired immunity.

Full recovery

• marks the end of disease syndrome and return to full health which is still under research.

Peter M.Wanjau

Public Health Officer