The Spectrum of Disease and The Iceberg Phenomenon

The spectrum of disease refers to the range of manifestations and severities of illness associated with a given diseases, illnesses, or injury. For example, HIV infection has broad clinical spectrum, from inapparent* to severe and fulminating**. 

The iceberg phenomenon describe a situation in which a large percentage of a problem is subclinical, unreported, or otherwise hidden from view. Thus, only the "tip of the iceberg" is apparent to the epidemiologist. (Examples of the iceberg phenomenon are given in the text.) Uncovering disease that might otherwise be below "sea-level" by screening and early detection often allows for better disease control. Consider:

• For every successful suicide attempt there are many more unsuccessful attempts and a still larger number of people with depressive illness that might be severe enough to have them wish to end their lives. With appropriate treatment, depressives with suicidal tendencies would be less likely to have suicidal ideation and be less likely to attempt suicide.
• Reported cases of AIDS represents only the tip of HIV infections. With proper anti-retroviral therapy, clinical illness may delayed and transmission averted.
• Serious dog bite injuries often go undetected. For each fatal dog bite there are about 670 dog bite hospitalizations, 16,000 emergency department visits, 21,000 medical visits to other clinics, and 187,000 non-treated bites (Weiss et al., 1998; Figure 2.7). With effective recognition, animal control programs can be put into place to prevent dog bite injuries.

* There is a cohort of HIIV+ prostitutes in Nairobi, Kenya that tend to remain symptom-free.
** That is, death.