Iceberg Phenomenon

The disease in the community is represented graphically through the phenomenon of iceberg.

Thus the disease is compared with the iceberg which has a floating tip, waterline and the vast submerged portion.

According to the phenomenon, the waterline of the iceberg differentiates the apparent disease from the inapparent disease.

Ans. is ‘d’ i.e., Diagnosis can be made with available techniques 

o The hidden part of iceberg (i.e. submerged portion) constitutes latent, inapparent, presymptomatic and undiagnosed cases and carriers in the community.

o Its detection and control is a challange to modern techniques in preventive medicine.

Ans. is ‘d’ i.e., Chicken pox 

In some disease, a great deal of subclinical infection occurs ‑

i)      Rubella                       iii) Polio                                     v) Japanese encephalitis                     vii) Influenza

ii)       Mumps                       iv) Hepatitis A and B                  vi) Diphtheria

In chickenpox

-Inapparent infection is estimated to occur in no more than 5% of susceptible children”.

Ans. is ‘c’ i.e., Apparent and inapparent cases 

The “waterline” represents the demarcation between apparent and inapparent disease.

Ans. is ‘a’ i.e., Measles 

Iceberg phenomena is not seen in rabies, tetanus and measles.

Ans. is ‘c’ i.e. Mortality is 80-90% 

• Mortality is 20-40% (not 80-90%).

About other options

• Man to man transmission is not seen.

o Cases show tip of iceberg -> Ratio of overt disease to inapparent infection varies from 1 : 1000.

o Culex is a zoophilic mosquito.

Ans. is ‘a’ i.e., Rabies

Iceberg phenomenon of disease is not shown by rabies, tetanus and measles.

Ans. is ‘c’ i.e., More subclinical cases

Iceberg of disease

• Disease in a community may be compared with an iceberg.
• The floating tip of the iceberg represents what the physian sees in the community, i.e. clinical cases (Diagnosed case, symptomatic case or clinically apparent case).
• The vast submerged portion of the iceberg represents the hidden mass of disease, i.e. latent, inapparent, presymptomatic and undiagnosed cases and carriers in the community.
• The “waterline” represents the demarcation between apparent and inapparent disease.
• Epidemiologist is concerned with Hidden portion of iceberg whereas clinician is concerned with tip of iceberg.
• Screening is done for Hidden portion of iceberg whereas diagnosis is done for tip of iceberg.
• Iceberg phenomenon of disease is not shown by rabies, tetanus and measles.
• The clinician concerned only with the tip of iceberg, i.e symptomatic cases that are seen in clinical treatment, this can result in inaccurate view of the nature and causes of a disease results because the minority of the cases are studied (hidden cases :- submerged portion of ice berg is not studied) -3 Clinician’s Fallacy.
•   iseases with a great deal of subclinical infection (therefore have iceberg phenomenon) are :-

1. Rubella
2. Polio
   
3. Japanese encephalitis
4. Influenza
5. Mumps
6. Hepatitis A and B
   
7. Diphtheria

Ans. is ‘c’ i.e., Measles

Icebarg of disease

• Disease in a community may be compared with an iceberg.
• The floating tip of the iceberg represents what the physian sees in the community, i.e. clinical cases (Diagnosed case, symptomatic case or clinically apparent case).
• The vast submerged portion of the iceberg represents the hidden mass of disease, i.e. latent, inapparent, presymptomatic and undiagnosed cases and carriers in the community.
• The “waterline” represents the demarcation between apparent and inapparent disease.
• Epidemiologist is concerned with Hidden portion of iceberg whereas clinician is concerned with tip of iceberg.
• Screening is done for Hidden portion of iceberg whereas diagnosis is done for tip of iceberg.
• Iceberg phenomenon of disease is not shown by rabies, tetanus and measles.
• The clinician concerned only with the tip of iceberg, i.e symptomatic cases that are seen in clinical treatment, this can result in inaccurate view of the nature and causes of a disease results because the minority of the cases are studied (hidden cases :-. submerged portion of ice berg is not studied) → Clinician’s Fallacy.

In some disease, a great deal of subclinical infection occurs –

• Rubella  
• Polio         
• Japanese encephalitis   
• Influenza
• Mumps  
• Hepatitis A and B   
• Diphtheria