Smallpox: A single case is a medical emergency
Both airborne and contact isolation needed
The Centers for Disease Control and Prevention currently recommends the following infection control precautions for smallpox. The CDC is expected to issue a new guidance on smallpox response in the near future, and some of the information may be updated. The guidelines summarized below were developed in conjunction with the Association for Professionals in Infection Control and Epidemiology.1
Smallpox is an acute viral illness caused by variola virus. Smallpox is a bioterrorism threat due to its potential to cause severe morbidity in a nonimmune population and because it can be transmitted via the airborne route. A single case is considered a public health emergency. Acute clinical symptoms of smallpox resemble other acute viral illnesses, such as influenza. Skin lesions appear, quickly progressing from macules to papules to vesicles. Smallpox is transmitted via both large and small respiratory droplets. Patient-to-patient transmission is likely from airborne and droplet exposure, and by contact with skin lesions or secretions. Patients are considered more infectious if coughing or if they have a hemorrhagic form of smallpox.
Preventive measures: A live-virus intradermal vaccination is available for the prevention of smallpox. Since the last naturally acquired case of smallpox in the world occurred more than 20 years ago, routine public vaccination has not been recommended. Vaccination against smallpox does not reliably confer lifelong immunity. Even previously vaccinated persons should be considered susceptible to smallpox.
Infection control practices: For patients with suspected or confirmed smallpox, both airborne and contact precautions should be used in addition to standard precautions. Airborne precautions require health care providers and others to wear respiratory protection when entering the patient room. (Appropriate respiratory protection is based on facility selection policy; must meet the minimal standards for particulate [N95] respirators.) Contact precautions require health care providers and others to wear clean gloves upon entry into patient room and wear a gown for all patient contact and for all contact with the patient’s environment. Based on local policy, some health care facilities require a gown be worn to enter the room. Gown must be removed before leaving the patient’s room. Wash hands using an antimicrobial agent.
Patient placement: Patients with known or suspected smallpox should be placed in rooms that meet the ventilation and engineering requirements for airborne precautions, including door that remains closed; monitored negative air pressure in relation to the corridor and surrounding areas; and six to 12 air exchanges per hour. Health care facilities without patient rooms appropriate for isolation should have a plan for transfer of suspected or confirmed smallpox patients to neighboring facilities with isolation rooms. Patient placement in a private room is preferred. However, in the event of a large outbreak, patients who have active infections may be cohorted in rooms that meet appropriate ventilation and airflow requirements.
Postexposure issues: Postexposure immunization with smallpox vaccine (vaccinia virus) is available and effective. Vaccination alone is recommended if given within three days of exposure. Passive immunization (i.e., for complications of vaccination) is available in the form of vaccinia immune-globulin (VIG) (0.6ml/kg IM). If more than three days have elapsed since exposure, both vaccination and VIG are recommended. Vaccina tion is generally contraindicated in pregnant women and persons with immunosuppression, HIV infection, and eczema who are at risk for disseminated vaccinia disease. However, the risk of smallpox vaccination should be weighed against the likelihood of developing smallpox following a known exposure. VIG should be given concomitantly with vaccination in these patients. Follow ing prophylactic care, exposed individuals should be instructed to monitor themselves for development of flu-like symptoms or rash during the incubation period (i.e., for seven to 17 days after exposure) and immediately report to designated care sites selected to minimize the risk of exposure to others.
Reference
1. Association for Professionals in Infection Control and Epidemiology Bioterrorism Task Force and Centers for Disease Control and Prevention Hospital Infections Program Bioterrorism Working Group. Bioterrorism readiness plan: A template for healthcare facilities. 1999. http://www.cdc. gov/ncidod/hip/Bio/bio.htm.
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