Isolation and Quarantine - K. Park's Textbook of Preventive and Social Medicine

ISOLATION

Definition

Isolation is defined as:

"Separation, for the period of communicability of infected persons or animals from others in such places and under such conditions, as to prevent or limit the direct or indirect transmission of the infectious agent from those infected to those who are susceptible, or who may spread the agent to others."

It is the oldest communicable disease control measure.

Purpose

The purpose of isolation is to protect the community by preventing transfer of infection from the reservoir to possible susceptible hosts.

Types of Isolation

The type of isolation varies with the mode of spread and severity of the disease. There are four types:

Type	Description
Standard isolation	Basic precautions for all patients
Strict isolation	For highly contagious or virulent diseases
Protective isolation	Protects an immunocompromised patient from external pathogens
High security isolation	For extremely dangerous or exotic infections

For each patient, the relative risks to the patient and to others should be assessed and the appropriate type determined.

Duration of Isolation (Table 41, Park)

Disease	Duration of Isolation
Chickenpox	Until all lesions crusted; usually ~6 days after onset of rash
Measles	From onset of catarrhal stage through 3rd day of rash
German measles	None (except non-immune women in first trimester should not be exposed)
Cholera, Diphtheria	3 days after tetracyclines started / until 48 hours of antibiotics (or negative cultures)
Shigellosis / Salmonellosis	Until 3 consecutive negative stool cultures
Hepatitis A	3 weeks
Influenza	3 days after onset
Polio	2 weeks (adult), 6 weeks (paediatric)
Tuberculosis (sputum +ve)	Until 3 weeks of effective chemotherapy
Herpes zoster	6 days after onset of rash
Mumps	Until swelling subsides
Pertussis	4 weeks or until paroxysms cease
Meningococcal meningitis / Streptococcal pharyngitis	Until first 6 hours of effective antibiotic therapy completed

Important Points About Isolation

Hospital isolation is better than home isolation wherever possible.
Isolation is particularly difficult in rural areas. In some situations (e.g., cholera outbreaks), the entire village may have to be isolated.
Ring immunization - isolation can be achieved by encircling infected persons with a barrier of immune persons. This method eradicated smallpox globally in the 1960s-70s.
The duration of isolation is determined by the duration of communicability and the effect of chemotherapy on infectivity.

Limitations of Isolation

In diseases with large subclinical infection and carrier state (e.g., polio, hepatitis A, typhoid fever) - even the most rigid isolation will not prevent disease spread.
Futile if disease is highly infectious before diagnosis - e.g., mumps.
Isolation has failed in control of leprosy, tuberculosis, and STDs. In these diseases, the concept of physical isolation has been replaced by chemical isolation (rapid treatment at home, rendering cases non-infectious quickly).
Cases are usually reported after the disease has spread widely.
Isolation as a "barrier approach" is not as successful as imagined and may give rise to a false sense of security.
In modern disease control, isolation has been replaced by surveillance in most cases, because of improvements in epidemiological technologies.
Today, isolation is recommended only when the risk of transmission is exceptionally serious.

QUARANTINE

Definition

Quarantine has been defined as:

"The limitation of the freedom of movement of such well persons or domestic animals exposed to communicable disease for a period of time not longer than the longest usual incubation period of the disease, in such manner as to prevent effective contact with those not so exposed."

Quarantine measures are also applied by a health authority to ships, aircraft, trains, road vehicles, other means of transport or containers, to prevent the spread of disease, reservoirs of disease or vectors of disease.

Key Distinction: Isolation vs Quarantine

Feature	Isolation	Quarantine
Applied to	Infected/sick persons or animals	Healthy contacts (well persons exposed to infection)
Basis	Period of communicability	Longest usual incubation period
Status of person	Already ill / infectious	Apparently healthy but exposed

"In contrast to isolation, quarantine applies to restrictions on the healthy contacts of an infectious disease."

Types of Quarantine

(a) Absolute (Complete) Quarantine

As defined above - complete limitation of freedom of movement for the full incubation period.

(b) Modified Quarantine

A selective, partial limitation of freedom of movement.
Example: exclusion of children from school.

(c) Segregation

Defined as "the separation for special consideration, control or observation of some part of a group of persons (or domestic animals) from others to facilitate control of a communicable disease."
Example: removal of susceptible children to homes of immune persons.

Current Status of Quarantine

Quarantine was once a popular method of disease control but has declined in popularity.
With better techniques of early diagnosis and treatment, quarantine as a method has become outdated.
It has been largely replaced by active surveillance.

Historical Note

The word "quarantine" comes from the Latin quarantina (forty days). In the 14th century, the procedure was introduced in Europe to protect against importation of plague - ships, crews and travellers were held for 40 days. Individual rulers and States placed barriers against infection by detection and isolation of incoming travellers.

Context in Disease Control

Both isolation and quarantine are part of controlling the reservoir (the first link in the chain of infection). The broader measures of reservoir control include:

Early diagnosis
Notification
Isolation
Treatment
Quarantine
Surveillance
Disinfection

Source: Park's Textbook of Preventive and Social Medicine, 25th edition - Chapter on Epidemiology of Communicable Diseases

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