Temporal Dynamics and Spatial Analysis of Competing Dengue 2 Virus Strains in the Americas

Masters Thesis, Biology Dept., University of New Mexico, July 2010

Stacy O’Neil Scholle

“The dengue virus is the causative agent of an important re-emerging infectious dis- ease that has become increasingly significant in tropical America and the Caribbean due to the infiltration of a more pathogenic Asian/American strain of dengue serotype 2 into the population. This invading strain is responsible for epidemics of dengue hem- orrhagic fever, a life-threatening disease that was not previously a large public health concern in the region. Here, I create a historical map of the invasion and replacement of the endemic American strain of dengue 2 by the Asian/American strain, showing that the timing of invasion spans 25 years, and is highly variable in the region. In addition, I model the competitive dynamics of the two strains using differential equa- tion models. By calculating and comparing the basic reproductive ratio (R0) for the Asian/American and American strain of dengue 2, I identify potential evolutionary trade-offs between the two strains and the ecological circumstances that benefit one trade-off over another. Numerically solving my models help to understand possible mechanisms behind variable timing of invasion by the Asian/American strain. The fit- ness gain resulting from the Asian/American strains shorter latency period increases as the adult vector mortality rate increases, indicating that regions where adult mosquito death rate is high will select for the more virulent strain of dengue 2.”

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