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:
- 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.
- Adverse events
would be expected to be higher in an indiscriminate vaccination
campaign due to vaccination of persons with unrecognized contraindications.
- 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:
- Diagnose
and isolate patients early in the course of illness.
- Quickly identify
and vaccinate those individuals who’ve had close contact
with the patient.
- 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.
- 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:
- 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.
- Other face-to-face
contacts after the onset of fever in the smallpox patient.
- 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.
- Do they have
a fever?
- Any signs
of illness?
- 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:
- Demographics
(name, age, address, etc.).
- Vaccination
Status and History (previously smallpox vaccination, date, etc.).
- Health Status – (any
current symptoms that may indicate developing smallpox?).
- 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:
- Vaccine take
for contacts and their household members and other vaccinated
close contacts. Persons with no take should be revaccinated.
- Vaccination
should be repeated if vaccine take is not evident.
- 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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