Based on the information provided, the most likely title for Helena's research paper would be "The Unique Characteristics of the Puumala Virus and Its Potential Usefulness in Hantavirus Research."
The Puumala virus is a type of hantavirus that is primarily found in Europe and is transmitted to humans through contact with the urine and droppings of infected rodents. Compared to other hantavirus strains, the Puumala virus causes a milder form of disease known as nephropathia epidemica. However, the unique genetic makeup of the Puumala virus may hold important clues for scientists studying hantaviruses in general.
Therefore, Helena's research paper is likely to focus on the unique characteristics of the Puumala virus, and how this knowledge can be useful to scientists who study hantaviruses.