Table 1. A comparison of the inherent salient features of smallpox, polio, measles, and malaria infections that favour or impede elimination of the disease and the most effective past and current interventions.
| Feature | Smallpox | Polio | Measles | Malaria |
| Disease syndrome is recognized by the public | Yes | Yes (paralytic form) | Yes | Variable |
| Extent of clinical expression | 100% | <1% (many subclinical and nonparalytic cases) | ∼100% | Often low |
| Specificity of the clinical disease | High | High for paralytic disease; low for nonparalytic disease | Moderate | Often low |
| n serotypes or species | 2: V. major (high case fatality) and V. minor (low case fatality) | 3 | 1 | 5a |
| Reservoir | Humans | Humans | Humans | Humans (except for P. knowlesi)a |
| Transmissibility | Usually low to moderate | High | Very high | Variable |
| Seasonality | Yes (regional) | Yes (regional) | Yes (regional) | Often |
| Incubation period (d) | 12–14 | 6–20 | 9–13 | ∼12 |
| Immunity follows a single clinical infection | Yes | Yes (type specific) | Yes | Nob |
| Interventions | Vaccine (live) | Vaccines (live oral and killed parenteral) | Vaccine (live subcutaneous) | ITNs; ACTs; IRS; IPTp; IPTi |
a
P. falciparum, P. vivax, P. malariae, and P. ovale are restricted to human hosts. P. knowlesi, which mainly infects nonhuman primates, can also cause disease in humans following natural transmission.
b
However, the development of immunity against clinical disease follows repeated infections.
ACT, artemisinin combination therapy; IPTi, intermittent preventive treatment in infants; IPTp, intermittent preventive treatment in pregnancy; IRS, indoor residual spraying; ITN, insecticide treated bednets.