Isolation & Quarantine
Measures in Response to a Smallpox Emergency
Principles
of Isolation
Smallpox
Transmission
Smallpox is
most often transmitted through direct contact with respiratory
droplets. Transmission usually requires close, face-to-face contact.
Rarely the disease can be spread through airborne transmission
of infectious particles over greater distances, usually associated
with cases that have a cough, which is not a usual feature of smallpox.
Although rare,
airborne infection over longer distances did sometimes occur. Two
hospital outbreaks in Germany seem to have secondary cases arising
from airborne spread. In the hospital associated outbreak in Meschede,
Germany, a case of smallpox had been confined o his room before
being diagnosed with smallpox and transferred to the smallpox hospital.
In spite of his isolation, 19 further cases of smallpox occurred
on all three floors of the building in which the index case had
been housed before transfer to the smallpox hospital. Reasons airborne
transmission may have occurred include:
- Confined
to private room as a suspected typhoid fever case with contact
isolation not respiratory isolation.
- Smoke studies
showed fairly brisk air currents by heating currents within the
hospital that may have contributed to the distribution of air
from the patient’s room.
- The patient
had prominent cough.
Today’s
infection control practices and hospital ventilation engineering
controls are more strict and should prevent transmission by preventing
circulation of air from an isolation room to other areas of the
hospital if implemented appropriately.
Transmission
has occasionally been linked to fomite such as clothing or bedding
that has been contaminated by dried respiratory secretions or lesion
drainage of cases. Smallpox was rarely transmitted by fomites.
Although the vast majority of smallpox cases can be traced back
to close, face-to-face contact and not to fomite contact, this
study by Downie et al. Demonstrated that live variola virus could
be recovered from bedding and clothing used by smallpox patients
and therefore could serve as a possible source of infection. Transmission
to laundry workers by infected bedding/clothing was reported during
several outbreaks by Dixon and others. Wetting down the materials
or avoiding sorting prior to washing to prevent re-aerosolization
of dried secretions and decreased the risk for this type of transmission.
The environment
immediately around the patient (e.g. pillow, bedclothes) had the
highest percentage of positive cultures. This would correspond
to areas where respiratory droplets would be most likely to settle
and where pustule drainage contamination would be the greatest.
Goals
of Isolation and Infection Control
The goals of
isolation and infection control are:
- Protect the
community by removing infectious patients from the community
environment.
- Protect healthcare
workers who must come into contact and care for the patient.
- Protect other
patients in the hospital.
Isolation is
used for diseases that are transmitted through casual contact or
respiratory transmission. Strict isolation is used for highly infectious
agents that may travel long distances through the air or be caught
from cutaneous contact with sores or secretions. Strict isolation
requires: restriction to a private room with controlled air flow,
persons entering the room must wear gowns, gloves, and respirators
capable of filtering out micron-level particles.
Surgical masks
give no protection for respiratory isolation, which is used for
diseases such as tuberculosis that are spread through the inspiration
of infected particles, but have only limited spread through contact
with wounds or secretions.
Respiratory
isolation requires the same precautions as strict isolation, but
without the extensive gowning and gloving. Contact isolation is
for diseases that spread by direct contact and limited droplet
spread. It requires personal protective measures but not a controlled
air supply.
Administrative
Controls
Many of the
administrative infection control practices that are already utilized
in current day hospitals can reduce worker exposures and spread
within the hospital. If a suspected smallpox case is admitted to
a hospital, utilize vaccinated workers (if available) to care for
the patient until the diagnosis is established. People presenting
to a hospital with a fever and a rash should be placed in respiratory
isolation until an airborne infectious etiology is ruled out (as
is done when varicella or measles is suspected). Established infection
control procedures should be followed when dealing with potentially
infectious waste.
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