Pre-Event Planning

Pre-Event Training

The first step to establishing surveillance for smallpox is in training health care providers and public health staff on the disease itself, how to efficiently diagnose and differentiate the disease, and the laboratory testing used to confirm it. Pre-event training should include:

  1. Clinical case definition.
  2. Differential diagnosis of febrile vesicular pustular rash illness.
  3. High level of alertness for cases of smallpox.
  4. Laboratory diagnostic issues (VZV, others).
  5. Notification procedures.
  6. Post-event surveillance methods (Case search and Contact Tracing).

Public health authorities should have systems and protocols in place to interview the case and manage their contacts and the contacts of contacts through a series of interviews and follow-up activities. Preparations for the following should be completed during pre-event training.

  1. Case interview.
  2. Contact identification.
  3. Contact households, other sites, travel modes.
  4. Contact risk category for prioritization.
  5. Assignment of contacts to tracing teams.
  6. Contact and contact household member interviews.
  7. Vaccination of contact and household members.
  8. Contact surveillance for fever/rash follow-up.
  9. Reporting of contacts with fever and rash for isolation.
  10. Vaccine take and severe adverse event surveillance.
  11. Reporting of severe adverse vaccination events.
  12. Maintaining forms and data files.
  13. Data reporting.

Pre-Event Smallpox Surveillance Clinical Case Definition

The following is the clinical case definition for smallpox during a pre-event period. This definition is slightly more broad than the standard case definition in the hopes that it will be more sensitive in catching a first case.

VARIOLA DEFINITION: An illness with acute onset of fever > 101¾F followed by a rash characterized by firm, deep-seated vesicles or pustules in the same stage of development without other apparent cause. Since varicella (chickenpox) is the illness most commonly confused with smallpox, it is important to learn this definition, as well. Remember that the smallpox rash will have a different appearance and feel than varicella.

VARICELLA DEFINITION: An illness with acute onset of diffuse (generalized) maculopapulovesicular rash without other apparent cause.

Since it’s the disease most often confused for smallpox, it will be important to understand the epidemiology of varicella in order to determine the likelihood of a rash illness being smallpox. In the United States, the comparison was found to break down in interesting ways.

Both diseases (at least when smallpox was naturally occurring) are most commonly seen in the spring. While smallpox age ranges can be in any group, current varicella epidemiology finds them mostly in children, with only a small percentage of cases occurring in adults. With smallpox, we consider the entire population to be susceptible. However, previous immunity might remain among adults who were previously vaccinated. Although rapidly changing after the introduction of varicella vaccine, the most cases still occur among young children, with very few adults susceptible, except for adults in tropical countries. Both diseases are more severe at the extremes of age and among the immunocompromised, yet smallpox causes ten times more fatalities. For all those fatalities, however, varicella is much more infectious. Smallpox vaccine is no longer routinely recommended, whereas a relatively new varicella vaccine is rapidly gaining acceptance and changing the epidemiology of the disease.

Because very few healthcare providers currently working have experience with smallpox and the early symptoms are indicative of so many other diseases, we know we will miss the first few cases. However, the pursuit of false positives can cost public health a lot in both personnel and funding when, at this time, we know that many of the rashes we’ll see are more likely to be caused by varicella, disseminated herpes zoster or enteroviral infections. If after going through the rash illness algorithm, a case is considered to be suspect smallpox, it will mean a public health emergency. Laboratory testing should be obtained immediately so that the appropriate interventions can begin.

Public health authorities also need to prepare their surveillance by ensuring that there is someone dedicated to coordinating all surveillance activities and that there are several different mechanisms that are in place for reporting cases; such as standard physician reporting, as well as laboratory reporting. This may or may not be possible, but where it can be established, redundant mechanisms can help to capture suspicion as early as possible. 

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