Britannica
Sources used in this answer
- immune system disorder - Immune deficiencies
- infectious disease - Natural and acquired immunity
- human disease - Predisposition of the host
- childhood disease and disorder - Physiological differences
- Questions About COVID-19 Answered - Why are older adults and those with underlying illness at greatest risk of COVID-19 infection?
- human disease - Heredity and environment
- human genetics - Other traits
- infectious disease - Family patterns
Which host factors can increase vulnerability to infectious disease?
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disease
A doctor examining chest X-rays of patients infected with tuberculosis, which remains one of the world's deadliest diseases.
Vulnerability to infectious disease is determined by a complex interplay between the host's biological state and environmental factors. Key host factors that increase susceptibility include:
- Age: Infancy and old age are periods of maximum vulnerability. In infants, the immune system is still maturing, while in older adults (typically over age 60 or 70), immune function often declines, reducing the body's ability to fend off pathogens.123
- Immune Status: Individuals with immune deficiencies—whether hereditary, developmental, or acquired through disease (such as HIV) or medical treatments—are at higher risk. Immunosuppressive drugs, while necessary for organ transplants or autoimmune conditions, intentionally compromise the immune system, leaving patients vulnerable to even low-virulence organisms.41
- Nutrition: Poor nutrition can undermine the immune system, weakening the body's natural defenses.41
- Underlying Health Conditions: Metabolic disorders like diabetes and other chronic illnesses can impair immune responses, increasing susceptibility to infection and complications.12
- Genetics: An individual’s genetic constitution can influence their susceptibility to specific infections, such as tuberculosis, by dictating the chemical basis for how the host responds to environmental pathogens.56