Isolation & Quarantine Measures in Response to a Smallpox Emergency

Isolation in Practice

When possible, it is preferable to have patients and contacts willingly submit to isolation and quarantine. Fewer public health and police resources would be needed. However, when necessary, both isolation and quarantine can be invoked under existing laws with law enforcement authorities assisting in its implementation. Isolation and quarantine as a necessary control measure for smallpox is inherent as preventing contagious individuals from transmitting disease to susceptible individuals is an important step for all transmissible diseases. However, it may not be feasible as the only control measure.

Modeling by Meltzer et al. that looked at control measures to contain an outbreak with 100 people initially infected showed:

  1. By using isolation/quarantine (or removal of contagious individuals) alone, it would take an estimated 240 days to contain the outbreak, with a resultant 2,300 cases. But, would require that a 50% removal rate of infectious cases be maintained. This high a removal rate may be very difficult to achieve.
  2. Also the use of quarantine alone at that level may not be acceptable in today’s society. Preparations must be made for all levels of interventions.
  3. Vaccination alone could also be effective, however, vaccination coverage would have to be sufficient to reduce the transmission rate from 3/case to less than 1/case; this could also be a difficult target to achieve.
  4. With a combination strategy that only achieved 25% removal or a reduction of transmission of 3/case to 2/case (much more achievable targets), the outbreak could still be terminated within 1 year. Any increase in either the percent removal or the reduction in transmission via vaccination coverage would decrease the number of cases and shorten the time interval to contain the outbreak.

Theoretically, quarantine alone can stop an outbreak. However, the level of quarantine that would be necessary according to some outbreak models, may be impossible to achieve and enforce with large numbers of people. Relying solely on either a vaccination or quarantine strategy alone is probably unwise. Combining the two would be the most reasonable and achievable strategy, given limited vaccine and personnel resources.

Planning of control strategies should take into account various numbers of cases and various levels of rates of transmission. Smaller numbers of cases with lower transmission rates could be controlled with isolation of cases and a smaller amount of vaccine and lower amounts of vaccine. Larger numbers or higher transmission rates would require more vaccine, if appropriate amounts of vaccine were unavailable, quarantine and isolation may become a greater part of the control strategy and resources would have to be available to implement these measures to a greater degree. Planning for any scenario should include how to intervene as quickly as possible.

Isolation would be instituted for individuals with smallpox and those potentially infectious. The level of isolation requirements would depend upon resources and facilities and the degree to which the community is affected (number of cases, etc.). Those who are known or presumed to be infectious should be placed in a facility like those previously discussed, where contact with non-protected (non-vaccinated) individuals can be prevented. Those contacts who are febrile, but who have not developed a rash, can be placed in an isolation facility or may be monitored at home for the development of rash if this can be done easily and in a manner that will prevent unvaccinated individuals from entering the home and the person from leaving the home until it is determined they do not have smallpox. Those contacts who are asymptomatic can be monitored for symptoms in their own home with travel restrictions. Example travel restrictions would be distance restrictions that keep them close enough to their home such that they could return to home via ground transportation (preferably in their own vehicle and not via public transportation so that others would not be exposed) within 1-2 hours if they were to develop a fever (note: air transportation that would allow a person to return home within a few hours would not be considered acceptable).

The numbers of these types of individuals (numbers of cases, numbers exposed, etc.) and the community resources would then help to shape the other population-wide response and control measures that may be implemented.

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