Smallpox Outbreak Control Activities and Strategies

Isolation and Quarantine (22:V1:60)

Smallpox is transmitted by respiratory droplets and through contact with secretions from smallpox lesions. Droplets can spread about 6 feet and can remain viable for a few hours. Isolation of smallpox patients should involve infection control measures to prevent:

  1. The sharing of air between a smallpox patient and a person susceptible to disease (respiratory isolation and precautions).
  2. Transmission of the virus to the healthcare provider by direct contact or to others from a healthcare provider with contaminated clothing (contact isolation and precautions).
  3. Others from coming into contact with infectious materials from the patient (infection control for waste disposal and decontamination measures).

Goals of Smallpox Isolation

The primary goal of smallpox isolation is to protect others from becoming infected. Groups such as healthcare personnel, response personnel, and other patients require protection from a smallpox patient.

It is imperative that the smallpox patient is isolated. Isolation includes preventing the sharing of airspace (respiratory isolation), preventing direct contact (by using protective clothing) and preventing contact with infectious materials (decontamination).

Respiratory Isolation

Respiratory isolation can be accomplished by placing the patient in negative pressure isolation rooms. Respirators are required for unvaccinated care-providers. Proper respiratory isolation is such that there are at least 6 to 12 air changes per hour, the air is vented to the outside, and air is not re-circulated to other rooms or areas.

Respiratory protection for patients with suspected or confirmed smallpox, both Airborne and Contact Precautions should be used in addition to Standard Precautions. Airborne Precautions apply for patients infected with microorganisms potentially transmitted by airborne droplet nuclei 5 microns or smaller. These evaporated droplets contain bugs, that can remain suspended in air, and be widely dispersed by air currents. The respirator should at least meet the NIOSH standard for particulate respirators, type N95. This is the same recommendation that has been made for protecting health care workers against tuberculosis infection.

If the outbreak produces large numbers of patients that can’t be accommodated in existing negative pressure rooms, or if no such rooms exist, the patients should be isolated in separate facilities, since there have been documented cases of smallpox transmission in patients housed two floors below. If groups of suspected patients are isolated in a facility designated only for care of smallpox patients, the:

  1. Special isolation rooms are not needed.
  2. Make sure that ventilation system (including heating and air conditioning systems) are not shared with any other facility.
  3. All persons entering facility must have been successfully vaccinated recently (including patients admitted to facility)

Personal Protective Equipment

Personnel should use disposable gloves, gown, and shoe covers for all contact with patients. This precaution is to prevent inadvertent transmission of variola virus form clothing or other contaminated items. Personnel should remove and correctly dispose of all protective clothing before contacting with other people.

Reusable bedding and clothing can be autoclaved or laundered in hot water with bleach to inactivate the virus. People who come into contact with materials potentially contaminated with smallpox virus, such as laundry handlers, housekeeping, and laboratory personnel should utilize appropriate protective equipment. If a case of smallpox is confirmed, these personnel should be vaccinated before handling contaminated materials.

Isolation Strategies

In a smallpox outbreak, there are 3 groups to consider when formulating isolation strategies. The first group is confirmed or suspected cases that would be considered immediately infectious to others. The second group is vaccinated contacts to smallpox cases that become febrile and may be developing smallpox or may be febrile from the vaccination or some other reason (potentially infectious). The final group is vaccinated contacts to smallpox case that don’t have any symptoms but who are still in the surveillance period for the development of smallpox (not currently infectious but could still develop smallpox)

Febrile vaccinated contacts must be isolated to assure that they are not experiencing a fever because they have contracted smallpox. This precaution is needed because the first stages of smallpox rash (the time when the patient become contagious) may be quite subtle.

Recently vaccinated contacts to smallpox cases that do not have any symptoms (FEVER) are not infectious so don’t require facilities with any special ventilation. They can be monitored in their home for development of a fever (check at least twice a day). Individuals in this group can be asked to stay at home during surveillance period for symptoms or may be allowed to travel outside of home if distance is restricted such that a quick return to home is possible if develops fever. All others staying in home must be vaccinated in case the contact develops smallpox. Other household members with vaccination contraindications that can’t be vaccinated to protect themselves if the contact does develop smallpox while at home under surveillance should stay elsewhere until the contact is no longer at risk of developing the disease. 

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