A study reported in NAM aidsmap concluded that dried blood containing hepatitis C virus (HCV) remained infectious for up to six weeks at normal room temperature. Researchers from Yale University tested the hypothesis that individuals who did not receive blood, blood products, or invasive procedures could acquire HCV infection through contact with the virus in dried blood spots on surfaces and objects.
The researchers conducted experiments to determine how healthcare workers or patients could contact infectious HCV in dried blood on surfaces. They dried blood spots with infectious HCV titres onto plates that they stored for six weeks at the following temperatures: 4, 22, and 37 degrees Celsius (C). The researchers used a testing assay and recovered potentially infectious HCV from dried blood spots stored at 37 degrees C for up to seven days. They recovered replicating HCV after six weeks of storage at 4 and 22 degrees C. The infectivity of HCV in the blood dropped in the first two weeks at 4 and 22 degrees C, but remained at low levels for up to six weeks. When researchers tested blood spots with higher HCV titres, almost all spots stored at 4 and 22 degrees C were potentially infectious after three weeks of storage. After 10 days of storage, all spots stored at 37 degrees C had replicating HCV.
The researchers tested the ability of three antiseptics—bleach, cavicide, and ethanol—to reduce infectivity of HCV blood spots. The antiseptics were very effective. One minute of bleach exposure at a 1:10 dilution ratio was 100-percent effective in destroying HCV. Cavicide at the same concentration was 94-percent effective, and ethanol (70 percent) destroyed HCV in 87 percent of blood spots. The antiseptics were significantly less effective when used at concentrations below recommended levels.
The researchers concluded that HCV can remain infectious at room temperatures for up to six weeks and may explain the incidence of hospital-acquired HCV infections and the high HCV incidence among injecting drug users.
The full report, “Hepatitis C Virus Maintains Infectivity for Weeks After Drying on Inanimate Surfaces at Room Temperature: Implications for the Risk of Transmission,” was published online in the Journal of Infectious Diseases (2013; doi: 10.1093/infdis/jit648).