Epidemiological Investigation

After the diagnosis of a patient with smallpox in a community, especially if it is the first case confirmed in the United States, the state epidemiologist or designee should coordinate an epidemiological investigation in collaboration with federal authorities and law enforcement. The investigation will determine the initial source of the outbreak, the population at risk, and the epidemiological features of the outbreak. If indicated, this investigation may be performed alongside contact identification and verification activities.

Monitor Outcome of Confirmed Cases

Work with medical providers to monitor the outcome of patients with confirmed smallpox. Report aggregate data to the state epidemiologist or designee.

Contact Tracing

The Clinical Guidance for Smallpox Vaccine Use in a Postevent Vaccination Program [PDF – 32 pages] defines a contact of a smallpox patient as:

  • Household family members of the smallpox patient
  • Others spending ≥3 hours in the household since the patient’s onset of fever
  • Non-household members with ≥3 hours of contact <2 meters (<6.5 feet) from a patient with a rash

Start contact tracing activities as soon as possible after a patient has been diagnosed with smallpox.

  • Interview the patient – Review the patient’s travel history for the previous 2 to 3 weeks. If more people are diagnosed with smallpox, this information will help determine a common source of exposure. Identifying the source of exposure will help to estimate the number of people at risk for illness.  Also identify other people the patient has had close contact with since their symptoms began (when the patient became infectious). The interviewers should be vaccinated prior to, or within 72 hours (preferably within 24 hours), of their first contact with the patient and wear appropriate personal protective equipment (PPE). If there is suspicion the smallpox emergency is the result of a deliberate release of the virus, the Federal Bureau of Investigation (FBI) and law enforcement agencies may need to collaborate on these interviews.
  • Identify contacts of the patient and their own close household contacts – Interview and assess contacts for symptoms. If any show symptoms of smallpox, arrange for their transport to the healthcare facility in the community designated to care for suspected smallpox cases. As long as those being interviewed do not show symptoms or have a fever, interviewing personnel do not need to wear PPE.
  • Vaccinate contacts and their household contacts – Give all contacts and their respective close household contacts information about where and when they can get the smallpox vaccination. Arrange for transportation to the place to receive the vaccination, if necessary. Provide a time and place for a vaccine “take” reading 6 to 8 days after vaccination. Also provide vaccinated contacts with a way to report their temperatures to designated public health officials.
  • Monitor vaccinated contacts for 14 to 18 days – Establish a dedicated phone line or other method for vaccinated contacts to report their temperature readings each day (fever surveillance). Contacts who do not have symptoms should take their temperatures twice every day (every 12 hours) for 18 days after their last contact with the smallpox patient, or 14 days after being vaccinated, whichever comes first. Contacts should report their temperatures to the designated public health official daily. If the contact develops a fever ≥101°F (38.3°C) for 2 successive readings, they should notify health department personnel and remain at home until transportation to the healthcare facility in the community designated to care for suspected smallpox cases can be arranged. Designate personnel to follow up with contacts who do not report regularly. Provide contacts information about how to seek care for and report adverse events to vaccination.
  • Monitor unvaccinated contacts for 18 days – Any contact or other person deemed as high risk for developing smallpox who refuses vaccination should undergo fever surveillance and remain at home for 18 days after their last known exposure to the smallpox virus.