LECTURE BY LECTURE BY DR SADF AKHTERDR SADF AKHTER

““ICE BERG PHENOMENON”ICE BERG PHENOMENON”

WHO Definition of WHO Definition of HealthHealth

Health is a state of Health is a state of complete physical, mental complete physical, mental and social well-being and and social well-being and not merely an absence of not merely an absence of disease or infirmitydisease or infirmityand ability to lead socially and and ability to lead socially and

economically productive lifeeconomically productive life..

Concept of diseaseConcept of disease

It is departure from It is departure from state of health state of health interrupting in normal interrupting in normal function of the bodyfunction of the body

Iceberg Iceberg PhenomenaPhenomenaof disease of disease That the “iceberg of disease” That the “iceberg of disease”

is a metaphor emphasising is a metaphor emphasising that for virtually every that for virtually every health problem the number health problem the number of cases of disease of cases of disease ascertained (those visible) ascertained (those visible) is outweighed by those not is outweighed by those not discovered (those invisiblediscovered (those invisible).).

Iceberg Iceberg PhenomenaPhenomenaof diseaseof disease The iceberg phenomenon The iceberg phenomenon

thwarts attempts to thwarts attempts to assess the burden of assess the burden of disease and the need for disease and the need for services, as well as the services, as well as the selection of representative selection of representative cases for study.cases for study.

Iceberg Iceberg PhenomenaPhenomenaof diseaseof disease This leads to what has This leads to what has

been called the in which been called the in which an inaccurate view of the an inaccurate view of the nature and causes of a nature and causes of a disease results from disease results from studying the minority of studying the minority of cases of the diseasecases of the disease..

Iceberg Iceberg PhenomenaPhenomenaof diseaseof disease Iceberg phenomenon of

disease gives a picture of the spectrum of diseases in a community.

The visible part of the iceberg denotes the clinically apparent cases of disease in the community.

Iceberg Iceberg PhenomenaPhenomenaof diseaseof disease The part of the iceberg below

the water level denoted the latent, subclinical, undiagnosed and carrier states in the community, which forms the major part.

Some diseases exhibiting iceberg phenomenon: Diabetes Hypertension Malnutrition Polio Leprosy Malnutrition Anemia

Symptoms are just tip of Symptoms are just tip of ice bergice berg

Headache Headache Constipation Constipation Poor concentrationPoor concentration FatigueFatigue Anexiety /depressionAnexiety /depression InsomniaInsomnia Immune weaknessImmune weakness Arthritis / fibromyalgiasArthritis / fibromyalgias

CAUSES are CAUSES are Submerged PortionSubmerged Portion Chemical Chemical BacteriaBacteria ParasitesParasites Pestesides Pestesides SolventsSolvents AluminiumAluminium Lead Lead DyesDyes Staph Staph StrepStrep Malo0nic acidMalo0nic acid VirusesViruses Mercury Mercury

• Within a population, there may be a small subset that actually develops clinical symptoms whereas a larger proportion may be asymptomatic (not exhibiting any symptoms at all).

West Nile neuroinvasive West Nile neuroinvasive disease(WNND)disease(WNND)

Encephalitis, meningitis, myelitisEncephalitis, meningitis, myelitis

Increased risk with age & co-morbid Increased risk with age & co-morbid conditionsconditions

Reportable conditionReportable condition

<1% infections<1% infections

"iceberg phenomenon"

WNF (10-30%)

West Nile fever (WNF) West Nile fever (WNF)

No “overt” CNS involvementNo “overt” CNS involvement

Fever, rash, headache, myalgia, arthralgiaFever, rash, headache, myalgia, arthralgia

Not a reportable conditionNot a reportable condition

10 -30% infections10 -30% infections

"iceberg phenomenon"

Asymptomatic WNAsymptomatic WNinfection (70-90%)infection (70-90%)

Asymptomatic infectionAsymptomatic infection

Not reportable conditionNot reportable condition

Same virus / antibody kinetics Same virus / antibody kinetics

Life-long immunityLife-long immunity

Potential problem for blood Potential problem for blood banking & organ donationbanking & organ donation

70-90% infections70-90% infections

"iceberg phenomenon"

Spectrum of virulence

poliomyelitis in a child0.1-1% of infections are clinically apparent

rubella50% of infections are clinically apparent

rabies100% of infections are clinically apparent

The iceberg concept of infectious disease

asymptomatic infection

classical clinical disease

less severe disease

Iceberg/pyramid of Iceberg/pyramid of diseasedisease In most diseases, as with In most diseases, as with

the iceberg, the larger the iceberg, the larger presence lurks unseen, presence lurks unseen, unmeasured and easily unmeasured and easily forgotten.forgotten.

Epidemiology that forgets Epidemiology that forgets the iceberg phenomenon of the iceberg phenomenon of disease Is weak and disease Is weak and potentially misleading.potentially misleading.

Iceberg/pyramid of Iceberg/pyramid of diseasedisease Unidentified cases may be Unidentified cases may be

different to identified ones, different to identified ones, both in terms of the natural both in terms of the natural history or spectrum of disease. history or spectrum of disease.

Where symptoms and disease Where symptoms and disease progression and outcome are progression and outcome are related, the undiagnosed cases related, the undiagnosed cases are likely to be less severe.are likely to be less severe.

Iceberg/pyramid of Iceberg/pyramid of diseasedisease

When symptoms and signs are not When symptoms and signs are not evident in the early stages of evident in the early stages of disease, as in high blood pressure disease, as in high blood pressure or chronic glaucoma, undiagnosed or chronic glaucoma, undiagnosed cases may be just as severe as cases may be just as severe as diagnosed ones. diagnosed ones.

Epidemiological studies based on Epidemiological studies based on selected cases from the tip of the selected cases from the tip of the iceberg may give an erroneous iceberg may give an erroneous view. view.

Iceberg/pyramid : Iceberg/pyramid : severity of diseaseseverity of disease Prostate cancer based on Prostate cancer based on

cases diagnosed in hospital cases diagnosed in hospital would lead to the view that would lead to the view that the disease is usually, if not the disease is usually, if not always, progressive. always, progressive.

Unselected cases show that Unselected cases show that prostatic cancer can in some prostatic cancer can in some cases be a static, or slowly cases be a static, or slowly progressive, phenomenonprogressive, phenomenon. .

Patients who are at the tip of the Patients who are at the tip of the iceberg are more likely to have iceberg are more likely to have multiple health problems than multiple health problems than others. others.

People with cardio-respiratory People with cardio-respiratory problems and diabetes are more problems and diabetes are more likely to be admitted to hospital, likely to be admitted to hospital, than people with only one of these than people with only one of these two problems. two problems.

Figure 6.6 The pyramid and iceberg of disease

1 Diseased, diagnosed & controlled

2 Diagnosed, uncontrolled

3 Undiagnosed or wronglydiagnosed disease

4 Risk factors for disease

5 Free of risk factors

Diagnosed disease

Undiagnosed orwrongly diagnosed disease

Iceberg phenomena of Iceberg phenomena of DiseaseDisease

Figure illustrates this idea and Figure illustrates this idea and develops the iceberg concept in develops the iceberg concept in the form of a pyramid of disease the form of a pyramid of disease by using its clear structure and by using its clear structure and shape. shape.

Blocks 1 and 2 correspond to the Blocks 1 and 2 correspond to the iceberg above the sea-level and 3 iceberg above the sea-level and 3 to 5 below sea level.to 5 below sea level.