Trajectory analysis of winds and vesicular stomatitis in North America, 1982-5.

This research article explores the possibility of wind playing a significant role in spreading vesicular stomatitis, a viral disease, across parts of Northern America between 1982-5, with hypotheses supported by virus isolates and climatic patterns.

Background

• The vesicular stomatitis virus (serotype New Jersey) prompted epidemic outbreaks in the United States and northern Mexico from 1982 to 1985.
• These outbreaks were not due to the introduction of disease by infected animals. Thus, the researchers sought to understand other possible transmission pathways, focusing specifically on possible airborne transmission by wind.

Methodology

• The research utilized backward trajectories of winds during these years to determine potential sources and spread patterns of the disease.
• The study also took into consideration the various climate conditions, including temperature and rainfall, which could aid in the spread of the disease.

Key Findings

• The study indicates that wind patterns could possibly be responsible for spreading vesicular stomatitis from northern Mexico to several states in the US. The pattern of wind-driven dispersal mirrors the succession of infection, starting in Arizona and New Mexico, continuing to Colorado and Utah, and ultimately reaching Wyoming, Idaho, and Montana.
• The researchers found a correlation between the arrival of the trajectories and weather events such as passage of a front and rain or simply the passage of a front or rain alone. During such trajectories, temperatures of 10 degrees Celsius and above were recorded at heights up to 2500-3500m.
• However, introducing the disease via airborne particles seemed improbable. To do so would require a source of at least 10(5) infectious units per minute per animal which is quite high.

Role of Simulium and Culicoides

• The virus had been isolated from two insects, Simulium and Culicoides during this epidemic.
• The amount of virus found in Simulium was sufficient to suggest biological transmission, pointing to the possibility that these insects, once infected, could have been carried downwind, effectively spreading the disease.
• The role of these insects in the disease’s pathogenesis and in relation to their behaviour is discussed further in the paper.

Implications

• The research highlights the complex interplay of viral transmission, atmospheric conditions, and insect vectors, and underscores the potential role of wind in spreading disease over large geographical areas.