Smoking is a major risk factor for acute respiratory tract and other systemic infections (see Table 2-5); active and passive smoke exposure increases the risk of infection (Arcavi and Benowitz, 2004). The mechanisms by which smoking increases risk are multifactorial and include structural and immunologic alterations (US Surgeon General, 2004). Smoking suppresses immune responses and impairs host defenses, such as removal of contaminants from the respiratory tract (Mehta et al., 2008). It also produces a chronic inflammatory state, including chronic bronchitis and aggravation of asthma. Smokers are more likely to become ill with and die from influenza and bacterial pneumonia (US Surgeon General, 2004); those who become ill have more serious illnesses, are more likely to be hospitalized, and lose more workdays.

Smoking has been associated with increased risk of Legionnaire’s disease, meningococcal meningitis, tuberculosis, and other infectious diseases (Arcavi and Benowitz, 2004). Smoking is a substantial risk factor for pneumococcal pneumonia, especially in patients with chronic obstructive pulmonary disease (COPD). Smoking is strongly associated with invasive pneumococcal disease in otherwise healthy adults and with a nearly twofold increased risk of community-acquired pneumonia, with 32% of the risk attributable to smoking (US Surgeon General, 2004).

The risk of developing and the severity of viral infections including the common cold, influenza, and varicella pneumonia are also increased in smokers. Influenza infections are more severe with more coughing, acute and chronic phlegm production, shortness of breath and wheezing in smokers. Influenza infections produce more work-loss days in smokers compared to nonsmokers. Smokers are at greater risk of

TABLE 2-5 Smoking and Infection

Type of Infection

OR (95% CI)

Pneumococcal pneumonia

2.6 (1.9–3.5)

Legionnaire’s disease

3.5 (2.1–5.8)

Meningococcal disease

2.4 (0.9–6.6)

Periodontal disease

2.8 (1.9–4.1)

Common cold

1.5 (1.1–1.8)


2.4 (1.5–3.8)

HIV infection

3.4 (1.6–7.5)


4.5 (4.0–5.0)

SOURCE: Adapted from Arcavi and Benowitz (2004).

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