STUDY QUESTIONS 21 DAY QUARANTINE PERIOD FOE EBOLA
As medical personnel and public health officials are responding to the
first reported cases of Ebola Virus in the United States, many of the safety
and treatment procedures for treating the virus and preventing its spread are
being reexamined. One of the tenets for minimizing the risk of spreading the
disease has been a 21-day quarantine period for individuals who might have been
exposed to the virus. But a new study by Charles Haas, PhD, a professor in
Drexel's College of Engineering, suggests that 21 days might not be enough to
completely prevent spread of the virus.
Haas's study "On
the Quarantine Period for Ebola Virus," recently published in PLOS
Currents: Outbreaks looks at the murky basis for our knowledge about
the virus, namely previous outbreaks in Africa in 1976 (Zaire) and 2000
(Uganda) as well as the first 9 months of the current outbreak.
In both cases, data
gathered by the World Health Organization reported a 2-21 day incubation period
for the virus -meaning that after 21 days if the individual hasn't presented
symptoms they are likely not to be infected or contagious. This is likely the genesis
of the Centers for Disease Control and Prevention's 21-day quarantine period,
but there is little indication from the CDC as to what other considerations
played into this policy.
"Twenty-one days
has been regarded as the appropriate quarantine period for holding individuals
potentially exposed to Ebola Virus to reduce risk of contagion, but there does
not appear to be a systemic discussion of the basis for this period," said
Haas, who is the head of the Department of Civil, Architectural and Environmental
Engineering at Drexel.
Haas suggests that a
broader look at risk factors and costs and benefits should be considered when
setting this standard. With any scientific data of this nature there is a
standard deviation in results -a percentage by which they may vary. In the case
of Ebola's incubation period the range of results generated from the Zaire and
Uganda data varied little. This might have contributed to the health
organizations' certainty that a 21-day quarantine period was a safe course of
action.
But looking more
broadly at data from other Ebola outbreaks, in Congo in 1995 and recent reports
from the outbreak in West Africa, the range of deviation is between 0.1 and 12
percent, according to Haas. This means that there could be up to a 12 percent
chance that someone could be infected even after the 21-day quarantine.
"While the 21-day
quarantine value, currently used, may have arisen from reasonable
interpretation of early outbreak data, this work suggests reconsideration is in
order and that 21 days might not be sufficiently protective of public
health," Haas said.
Haas, who has
extensive background in analyzing risk of transmitting biological pathogens,
explains that these quarantine periods must be determined by looking at the
cost of enforcing the quarantine versus the cost of releasing exposed
individuals. Looking at the potential tradeoff between costs and benefits as
the quarantine time is extended should guide public health officials in
determining the appropriate time. Obviously, with more contagious and
potentially deadly diseases the cost of making a mistake on the short side when
determining a quarantine is extremely high.
"Clearly for
pathogens that have a high degree of transmissibility and/or a high degree of
severity, the quarantine time should be greater than for agents with lower
transmissibility and/or severity. The purpose of this paper is not to estimate
where the balancing point should be, but to suggest a method for determining
the balancing point."
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