Survival of Lassa Virus in Blood and Tissue Culture Media and in a Small Particle Aerosol

Abstract

Knowledge of the survival and stability of a pathogen is important for understanding its risk, reducing its transmission, and establishing control measures. Lassa virus is endemic in West Africa, causes severe disease, and is an emerging pathogen of concern. Our study examined the survival of Lassa virus in blood and tissue culture media at two different temperatures. The stability of Lassa virus held within a small particle aerosol was also measured. In liquids, Lassa virus was found to decay more quickly at 30 °C compared to room temperature. Sealed samples protected from environmental desiccation were more stable than samples open to the environment. In a small particle aerosol, the decay rate of Lassa virus was determined at 2.69% per minute. This information can contribute to risk assessments and inform mitigation strategies in the event of an outbreak of Lassa virus.

Keywords: Lassa virus; aerosol; blood; stability; survival; tissue culture media.

Figure 1

Titre of Lassa virus in blood or tissue culture media over time. The persistence of Lassa virus in blood (top row, (A,B)) or tissue culture media, TCM, (bottom row, (C,D)) was measured over two days. Samples were stored at room temperature (RT, 19–22 °C, left, (A,C)) or 30 °C (right, (B,D)), open to the external environment (white circles) or sealed (black triangles). Experiments were performed on two separate occasions and the individual titres from three replicates per experiment are shown (n = 6 per condition). The limit of detection (LoD) of the TCID₅₀ assays is shown as a dotted line on each graph.

Figure 2

Aerosol survival of Lassa virus. (Left) Lassa virus was aerosolised in tissue culture media and held in a Goldberg Drum at medium relative humidity (50–60%). Impinger samples were taken at set time points and enumerated by TCID₅₀ assay. Three aerosol experiments were performed: each time-point was assayed in triplicate. Counts were adjusted for dilution effect of sampling and mean adjusted counts of each of the 3 experiments plus a best fit line are shown. The limit of detection (LoD) of the TCID₅₀ assays is shown as a dotted line. (Right) The theoretical decay of Lassa virus in TCM with decay as a percentage of starting amount shown. Horizontal lines at 50% represent half-life and at 10% give an indication of time for starting amount to drop by 90% (1× Log₁₀).