Post-Event Operational Issues

Contact Tracing and Follow-Up

An essential outbreak response activity is the identification and timely follow-up and vaccination of contacts to smallpox cases. Since smallpox is a contagious disease, once a case is confirmed, the highest priorities for public health officials are to reduce the risk of ongoing transmission by isolating the case to prevent exposure of others and identifying and vaccinating close contacts of the case. Any vaccination strategy for containing a smallpox outbreak should still utilize this concept. Vaccinating and monitoring a “ring” of people around each case and contact will help to protect those at the greatest risk of contracting the disease, as well as form a buffer of immune individuals to prevent the spread of disease.

This strategy is more desirable for the following reasons:

  1. Focused contact tracing and vaccination, combined with extensive surveillance and isolation of cases, was successful in stopping outbreaks in the eradication program and was the only strategy used for smallpox control in Australia.
  2. Adverse events would be expected to be higher in an indiscriminate vaccination campaign due to vaccination of persons with unrecognized contraindications.
  3. Current supplies of smallpox vaccine would be exhausted quickly if an indiscriminate campaign was utilized.

Ring Vaccination: Biologic Basis for Contact Tracing and Follow-Up

It is important to remember that smallpox is a contagious disease that spreads among susceptible individuals. Smallpox is transmitted predominately by droplets at relatively close range. Droplets travel “range” approximately 6feet/2meters. Individuals who have had close, prolonged contact with a smallpox patient are at the highest risk for developing infection. By priority vaccinating and monitoring these people, we can stop the chain of susceptible people who pass on the disease. Since the length of time and closeness of exposure increases risk for contacts to become infected, the main tracing and vaccination efforts should be focused on contacts we know are the most at risk (e.g. household contacts), to make the most efficient use of limited resources and staff to more efficiently stop the outbreak. It is important to remember that even if resources aren’t limited and/or a broader vaccination approach is implemented, it is still imperative that close contacts and their household contacts are identified, vaccinated, and monitored for the development of the disease.

In order to quickly interrupt the chain of transmission, there are several actions that must be taken:

  1. Diagnose and isolate patients early in the course of illness.
  2. Quickly identify and vaccinate those individuals who’ve had close contact with the patient.
  3. Vaccinate the people in close contact to the primary contact to the smallpox patient to provide a ring of protected people around that persons if they develop smallpox.
  4. Monitor the primary contacts for development of disease in order to quickly isolate them and begin the process of containment for them if needed.

We also need to vaccinate the contacts of those contacts who may have had less extensive contact with the case and who can provide an additional buffer from the patient, in the event the contact becomes ill. The contacts that should be identified first are:

  1. All who’ve had direct, face-to-face contact with the patient. Household members are usually at the highest risk because of the closeness and extended length of contact.
  2. Other face-to-face contacts after the onset of fever in the smallpox patient.
  3. The close contacts to the primary contacts (or contacts of contacts) should also be identified.

Factors Determining Risk of Transmission

People who spent more time with the patient, and people who had face-to-face contact of around six feet or less with the patient would be considered at risk for contracting the disease. Other factors that may be considered include characteristics of the smallpox case including clinical type, day of illness (infectiousness is highest in the first several days of rash onset), whether or not the patient had a cough etc.

Contact Management Overview

Contact management would require that a detailed interview of smallpox patient be conducted to establish known contacts and potential contacts. Determining contacts since onset of fever is important. Also, determine activities and movement of case in the 3-week period before onset of fever. This may help identify where the index case was exposed as well as additional cases if more people were exposed at the same time. A detailed interview of identified contacts should be conducted. This will help establish the level of risk for the contact, and provide additional clues as to the source of exposure for the case patient. Interviews also allows you to establish a relationship with the contact, who you will need to visit or contact at least daily during their monitoring period to ascertain their status (ill or not ill). Should also use this opportunity to assure that the contact and their contacts are vaccinated.

To monitor outbreak control efforts, a database should be established to track all cases and contacts. This will allow the outbreak to be better monitored, will put in some controls to assure appropriate case management, refine outbreak control strategies and might provide clues as to the source of the outbreak.

Interview and Risk Determination

When interviewing the contact, determine the health status of the contact.

  1. Do they have a fever?
  2. Any signs of illness?
  3. Any signs of rash that could indicate they are already developing smallpox?

Obtain a day-by-day history of the contact’s activities since the smallpox case developed their fever. If this correlates to some of the smallpox case’s activities, it could supply other contacts to the index case who haven’t been recognized for follow-up. Identify a list of contacts to the contact. They should explore household contacts, and other close, non-household contacts, in places outside of the house, such as work, school, etc. Household contacts of contacts should be vaccinated. May consider expanding vaccination to contacts outside of home if contact not confined to home during monitoring period for symptoms. This data should be maintained in a database for evaluation of the larger outbreak.

Contact Tracing Forms

Other questions that should be asked of the Contacts and their close contacts:

  1. Demographics (name, age, address, etc.).
  2. Vaccination Status and History (previously smallpox vaccination, date, etc.).
  3. Health Status – (any current symptoms that may indicate developing smallpox?).
  4. Adverse Reactions to previous smallpox vaccines?

Vaccination of Contacts

The highest priority cases for vaccination are contacts of cases and after that, their close contacts. Household members of contact should be screened thoroughly for contraindications to smallpox vaccine. Check for history of conditions such as eczema, immunosuppressive diseases or medications. If household contact with serious contraindications to vaccination and is not vaccinated, they should stay outside of home for duration of monitoring period so develops smallpox in the home. If vaccine is brought to the contact home, the contact and their household contacts should be vaccinated. Otherwise, the interviewer should assure that the contact and their household members are taken to an established vaccination site to receive vaccination.

If a smallpox patient went to work or school after the onset of fever, it may be difficult to identify all the people that had face-to-face contact so you should vaccinate everyone in the building during the time the patient was present. You could consider limiting your contact management to those whose work locations are close to the patient’s and those who worked directly with the patient if there was limited movement of the patient in the building.

Follow-Up and Surveillance

Contacts who do not have fever or rash at the time of interview must remain under active surveillance for 18 days after their last contact. Contacts must monitor and record their temperature in the morning and early evening of each day. Each day before 8pm, they must call or be called by a designated person (or staff at a designated phone number) to report their daily temperatures, health status, and any severe reactions following vaccination. During surveillance/monitoring period, health officials may elect to allow them to continue their usual daily activities as long as no temperatures of more than 101¾F (38¾C) are measured. They should not, however, travel away from their city of residence. If they have a temperature, they must remain in or immediately return to their own home. If they have two successive temperature readings of 101¾F (38¾C) or higher, they must contact health department personnel immediately, remain at home, and have contact only with vaccinated household members until they can be further evaluated.

On day 7 following vaccination, must confirm:

  1. Vaccine take for contacts and their household members and other vaccinated close contacts. Persons with no take should be revaccinated.
  2. Vaccination should be repeated if vaccine take is not evident.
  3. Serious adverse events should be reported

Organizing Contact Tracing and Follow-Up

Contact tracing teams (of 2 or more) are preferable to individuals if possible. This allows for a more efficient follow-up and could help improve security for the teams. Given the number of daily contacts any one person can have, public health authorities should be prepared to field numerous teams in order to quickly manage the contacts. Supervisory structure should be established in order to monitor activity and provide quality assurance. If the outbreak grows too large for the number of case management teams, the supervisory structure can prioritize team contact tracing activities according to the level of risk for different groups of contacts (e.g. focus only on household contacts).

A database should be established to record all contact information. A database would make it easier to determine spread and attack rates in order to improve epidemiologic response. This can help supervisors ensure that all known contacts receive follow-up. This can also help public health authorities better define their staffing needs. Databases will require data entry staff to support the teams, or technology that will allow the case managers to enter data while onsite (e.g. handheld PDAs, laptops, etc.)

Managing Large Case Counts

Fewer cases allow intensive follow-up of high, medium, and lower risk contacts and contacts of contacts, etc.

Many cases require that contact tracing concentrates on the highest risk contacts. The assumption being is that contact tracing/surveillance containment will reduce spread and in several generations the many cases will be reduced to few cases. (Attrition)

If enough vaccine is available, larger-scale community vaccination could be done in addition to high-risk contact identification and vaccination. This activity would increase the chances of achieving vaccination of contacts that weren’t previously identified, as well as decrease the number of people in the community at risk of disease if unidentified contacts develop smallpox. In the case of a large release mass vaccination, plus ring strategy around known cases is suggested. For a multi-focal release the same strategy as for a large release should be followed, as possible.

Public Confidence Relating to Contact Tracing and Follow-up

The general public may not understand the potential effectiveness of the ring vaccination strategy. They may also not understand why it should always be used, no matter what other vaccination strategies are employed. Most will expect and demand widespread vaccination, even if the outbreak is small. If population-wide vaccination is not possible or will not be used in an area in response to a smallpox outbreak, then public health authorities must conduct extensive pre-outbreak education programs to inform about the effectiveness and need for this strategy to prepare the community before the panic of a smallpox outbreak. 

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