Influenza virus affects millions of people across the globe every year. However only a fraction of these individuals experience symptoms, and only a fraction of symptomatic individuals are identified by a public health surveillance system and thus "counted" as a flu case. The lack of information regarding these silent influenza infections has limited our understanding of influenza dynamics and epidemic timing, especially in tropical parts of the world where there is no winter to herald the coming of the flu season.
Research led by CIDD’s Maciej Boni, as well as collaborators from Oxford University Clinical Research Unit (Ho Chi Minh City, Vietnam) and Erasmus Medical Center (Rotterdam, Netherlands), has focused on assessing past flu exposure via antibody response. Using 20,152 general–population serum samples from southern Vietnam collected between 2009 and 2013, they have developed novel statistical methods to describe the timing and distribution of H1N1 and H3N2 viral strains. Instead of a binary conclusion, exposure to influenza or not, they use a continuous titer measurement from a protein microarray assay. This antibody testing provides an unbiased way to measure flu prevalence, as well as approximate the timing of that individual’s infection. This is especially important in the tropics because flu infections are a combination of local persistence, annual/biannual outbreaks, and continuous circulation.
The next step for this team is to use confirmed case follow-up to determine if the antibody titer distribution conforms to the categories created through this analysis: recent, historical, and naïve. The methodology developed here can also be used to detect antibodies for 16 other influenza virus strains, revolutionizing the way disease can be monitored and studied in the tropics.
Synopsis written by Ellen Brandell
Photo caption: The H1N1 virus; from April 12, 2009 to April 10, 2010 approximately 60.8 million cases, 274,304 hospitalizations, and 12,469 deaths occurred in the United States due to H1N1 (information from CDC, photo from shutterstock)
N. Nhat, S. Todd, E. de Bruin, T. Thao, N. Vy, T. Quan, D. Vinh, J. van Beek, P. Anh, H. Lam, N. Hung, N. Thanh, H. Huv, V. Ha..
Structure of general-population antibody titer distributions to influenza A virus
Journal: Nature Scientific Reports