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Inferring Transmission Bottleneck Size from Viral Sequence Data Using a Novel Haplotype Reconstruction Method.

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Ghafari, Mahan 
Weissman, Daniel B 
Illingworth, Christopher JR  ORCID logo  https://orcid.org/0000-0002-0030-2784

Abstract

The transmission bottleneck is defined as the number of viral particles that transmit from one host to establish an infection in another. Genome sequence data have been used to evaluate the size of the transmission bottleneck between humans infected with the influenza virus; however, the methods used to make these estimates have some limitations. Specifically, viral allele frequencies, which form the basis of many calculations, may not fully capture a process which involves the transmission of entire viral genomes. Here, we set out a novel approach for inferring viral transmission bottlenecks; our method combines an algorithm for haplotype reconstruction with maximum likelihood methods for bottleneck inference. This approach allows for rapid calculation and performs well when applied to data from simulated transmission events; errors in the haplotype reconstruction step did not adversely affect inferences of the population bottleneck. Applied to data from a previous household transmission study of influenza A infection, we confirm the result that the majority of transmission events involve a small number of viruses, albeit with slightly looser bottlenecks being inferred, with between 1 and 13 particles transmitted in the majority of cases. While influenza A transmission involves a tight population bottleneck, the bottleneck is not so tight as to universally prevent the transmission of within-host viral diversity.IMPORTANCE Viral populations undergo a repeated cycle of within-host growth followed by transmission. Viral evolution is affected by each stage of this cycle. The number of viral particles transmitted from one host to another, known as the transmission bottleneck, is an important factor in determining how the evolutionary dynamics of the population play out, restricting the extent to which the evolved diversity of the population can be passed from one host to another. Previous study of viral sequence data has suggested that the transmission bottleneck size for influenza A transmission between human hosts is small. Reevaluating these data using a novel and improved method, we largely confirm this result, albeit that we infer a slightly higher bottleneck size in some cases, of between 1 and 13 virions. While a tight bottleneck operates in human influenza transmission, it is not extreme in nature; some diversity can be meaningfully retained between hosts.

Description

Keywords

influenza A, population bottleneck, transmission, Evolution, Molecular, Genetic Variation, Genome, Viral, Haplotypes, Humans, Influenza A virus, Influenza, Human, Models, Theoretical, Sequence Analysis, DNA, Viruses

Journal Title

J Virol

Conference Name

Journal ISSN

0022-538X
1098-5514

Volume Title

94

Publisher

American Society for Microbiology

Rights

All rights reserved
Sponsorship
Wellcome Trust (101239/Z/13/Z)
Isaac Newton Trust (Minute 18.23(i))
University of Helsinki