POSTEXPOSURE INFECTION CONTROL
Vol. 281 No. 22,
June 9, 1999
POSTEXPOSURE INFECTION CONTROL
A smallpox outbreak poses difficult public health problems because of
the ability of the virus to continue to spread throughout the population
unless checked by vaccination and/or isolation of patients and their
close contacts.
A clandestine aerosol release of smallpox, even if it infected only 50
to 100 persons to produce the first generation of cases, would rapidly
spread in a now highly susceptible population, expanding by a factor
of 10 to 20 times or more with each generation of cases.2, 10, 38
Between the time of an aerosol release of smallpox virus and
diagnosis of the first cases, an interval as long as 2 weeks or more is
apt to occur because of the average incubation period of 12 to 14
days and the lapse of several additional days before a rash was
sufficiently distinct to suggest the diagnosis of smallpox. By that
time, there would be no risk of further environmental exposure from
the original aerosol release because the virus is fully inactivated within
2 days.
As soon as the diagnosis of smallpox is made, all individuals in whom
smallpox is suspected should be isolated immediately and all
household and other face-to-face contacts should be vaccinated and
placed under surveillance. Because the widespread dissemination of
smallpox virus by aerosol poses a serious threat in hospitals, patients
should be isolated in the home or other nonhospital facility whenever
possible. Home care for most patients is a reasonable approach,
given the fact that little can be done for a patient other than to offer
supportive therapy.
In the event of an aerosol release of smallpox and a subsequent
outbreak, the rationale for vaccinating patients suspected to have
smallpox at this time is to ensure that some with a mistaken
diagnosis are not placed at risk of acquiring smallpox. Vaccination
administered within the first few days after exposure and perhaps as
late as 4 days may prevent or significantly ameliorate subsequent
illness.39 An emergency vaccination program is also indicated that
would include all health care workers at clinics or hospitals that might
receive patients; all other essential disaster response personnel, such
as police, firefighters, transit workers, public health staff, and
emergency management staff; and mortuary staff who might have to
handle bodies. The working group recommends that all such
personnel for whom vaccination is not contraindicated should be
vaccinated immediately irrespective of prior vaccination status.
Vaccination administered within 4 days of first exposure has been
shown to offer some protection against acquiring infection and
significant protection against a fatal outcome.15 Those who have been
vaccinated at some time in the past will normally exhibit an
accelerated immune response. Thus, it would be prudent, when
possible, to assign those who had been previously vaccinated to
duties involving close patient contact.
It is important that discretion be used in identifying contacts of
patients to ensure, to the extent that is possible, that vaccination and
adequate surveillance measures are focused on those at greatest
risk. Specifically, it is recommended that contacts be defined as
persons who have been in the same household as the infected
individual or who have been in face-to-face contact with the patient
after the onset of fever. Experience during the smallpox global
eradication program showed that patients did not transmit infection
until after the prodromal fever had given way to the rash stage of
illness.17, 18
Isolation of all contacts of exposed patients would be logistically
difficult and, in practice, should not be necessary. Because contacts,
even if infected, are not contagious until onset of rash, a practical
strategy calls for all contacts to have temperatures checked at least
once each day, preferably in the evening. Any increase in temperature
higher than 38°C (101°F) during the 17-day period following last
exposure to the case would suggest the possible development of
smallpox2 and be cause for isolating the patient immediately,
preferably at home, until it could be determined clinically and/or by
laboratory examination whether the contact had smallpox. All close
contacts of the patients should be promptly vaccinated.
Although cooperation by most patients and contacts in observing
isolation could be ensured through counseling and persuasion, there
may be some for whom forcible quarantine will be required. Some
states and cities in the United States, but not all, confer broad
discretionary powers on health authorities to ensure the safety of the
public's health and, at one time, this included powers to quarantine.
Under epidemic circumstances, this could be an important power to
have. Thus, each state and city should review its statutes as part of
its preparedness activities.
During the smallpox epidemics in the 1960s and 1970s in Europe,
there was considerable public alarm whenever outbreaks occurred
and, often, a demand for mass vaccination throughout a very
widespread area, even when the vaccination coverage of the
population was high.2 In the United States, where few people now
have protective levels of immunity, such levels of concern must be
anticipated. However, the US vaccine supply is limited at present;
thus, vaccine would have to be carefully conserved and used in
conjunction with measures to implement rapid isolation of smallpox
patients.
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The working group recommends that an emergency stockpile of at
least 40 million doses of vaccine and a standby manufacturing
capacity to produce more is a critical need. At a minimum, this
quantity of vaccine would be needed in the control of an epidemic
during the first 4 to 8 weeks after an attack.
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SUMMARY
The specter of resurgent smallpox is ominous, especially given the
enormous efforts that have been made to eradicate what has been
characterized as the most devastating of all the pestilential diseases.
Unfortunately, the threat of an aerosol release of smallpox is real and
the potential for a catastrophic scenario is great unless effective
control measures can quickly be brought to bear.
Early detection, isolation of infected individuals, surveillance of
contacts, and a focused selective vaccination program are the
essential items of a control program. Educating health care
professionals about the diagnostic features of smallpox should permit
early detection; advance regionwide planning for isolation and care of
infected individuals in their homes as appropriate and in hospitals
when home care is not an option will be critical to deter spread.
Ultimately, success in controlling a burgeoning epidemic will depend
on the availability of adequate supplies of vaccine and VIG. An
adequate stockpile of those commodities would offer a relatively
inexpensive safeguard against tragedy.
jama.ama-assn.org
Bet our brave congressmen/women and their families get vaccinated so that they can take care of Americas
business of burying the dead.
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Is smallpox a threat and is a vaccine available?
The last case of smallpox on earth occurred in Somalia, in 1977. In 1980, the World Health Organization certified that smallpox had been eradicated from the planet.
Currently, the only known remaining samples of smallpox virus are held in secure facilities at the Centers for Disease Control and Prevention in Atlanta, GA, and the Institute for Viral Preparations in Koltsovo, Russia. Although destruction of all remaining samples of smallpox virus has been proposed, the United States government has decided to permanently store its samples of smallpox virus. Allegations and rumors of smallpox virus stocks in other locations have not been verified.
As a result of the successful eradication program, smallpox vaccine was removed from the commercial market in 1983, and is no longer a licensed product in the United States. The United States Public Health Service maintains an emergency stockpile of approximately 15 million doses.
At the present time, smallpox vaccine is supplied only to certain laboratory workers who are at risk of infection with
smallpox-like viruses because of their occupation. The U.S. Food and Drug Administration does not allow the release of smallpox vaccine to any other person for any reason.
For more information on Smallpox, log onto bt.cdc.gov or
For the U.S. Public Health Service's Advisory Committee on Immunization Practices recommendations on smallpox
vaccination, log onto cdc.gov
vdh.state.va.us |
