Dried spots of
blood contaminated with hepatitis C virus (HCV) can remain infectious for up to
six weeks at normal room temperatures, research published in the online edition
of the Journal of Infectious Diseases
shows. Commercially available antiseptics reduced the infectivity of the blood
spots, but only when used at recommended concentrations.
“We observed that
HCVcc [cell culture] could maintain infectivity for up to 6 weeks at 4o
and 22o C,” write the authors. “Commercially available antiseptics
reduced the infectivity of HCV on surfaces only when used at the recommended
concentrations, but not when further diluted.”
The investigators believe
their findings could explain hospital-acquired HCV infections in individuals
who have not undergone surgery or received blood products, and also the ongoing
HCV epidemic among injecting drug users.
HCV is a
blood-borne virus. Injecting drug use is a well-known risk factor, and a large
number of individuals were infected with HCV after receiving blood or blood
products. But research suggests that hospital-acquired infections are occurring
among patients who did not receive blood/blood products or undergo an invasive
procedure. Investigators from Yale University hypothesised that this was due to
contact with infectious quantities of HCV in minute dried blood spots on
inanimate surfaces and objects.
performed a series of experiments to establish the circumstances in which healthcare
workers or patients could come into contact with infectious HCV dried on
surfaces. The investigators believe theirs is the first study to “closely
simulate” the conditions leading to hospital-acquired HCV infection.
Blood spots with
potential infectious HCV titres were dried onto plates and stored at
temperatures of 4oC, 22oC and 37oC for up to
six weeks. The authors also examined the effect of three commercially available
antiseptics – bleach, cavicide and ethanol – on the infectivity of the
HCV-contaminated dried blood spots.
Using a testing
assay with a detection limit of 1000 RLA, potentially infectious HCV was
recovered from dried blood spots stored at 37oC for up to
seven days. At temperatures
of 4oC and 22oC, replicating HCV was recovered for up to
six weeks of storage. The infectivity of the dried spots declined sharply
during the first two weeks of storage at these temperatures. Nevertheless,
potentially infectious quantities of HCV – albeit at low levels – continued to
be recovered for up to six weeks.
Blood spots with
higher HCV titres (106 infectious units/ml) were also tested. Almost
all spots stored at 4oC and 22oC remained potentially
infectious after three weeks of storage. After ten days of storage, 100% of
spots stored at 37oC also contained replicating HCV.
available antiseptics were highly effective against the HCV-contaminated blood
spots. One minute of exposure to bleach (diluted to a ratio of 1:10) was 100%
effective, whereas cavicide at a similar concentration was 94% effective and
ethanol (70%) eliminated HCV in 87% of blood spots. The effectiveness of these
disinfectants was significantly reduced when their concentrations were reduced
below recommended levels.
“There are several
commercially available antiseptics that are effective against HCV,” write the
They conclude that
HCV can remain infectious at room temperatures for up to six weeks, “a
biological basis for recent observational studies reporting increasing
incidence of nosocomial [hospital-acquired] HCV infections and continued high
incidence among people who inject drugs.”