Abstract
BackgroundCo-infection of different influenza A viruses is known to occur but how viruses interact within co-infection remains unknown. An outbreak in a college campus during the 2009 pandemic involved two subtypes of influenza A: persons infected with pandemic A/H1N1; persons infected with seasonal A/H3N2 viruses; and persons infected with both at the same time (co-infection). This provides data to analyse the possible interaction between influenza A viruses within co-infection.MethodsWe extend a statistical inference method designed for outbreaks caused by one virus to that caused by two viruses. The method uses knowledge of which subtype each case is infected with (and whether they were co-infected), contact information and symptom onset date of each case in the influenza outbreak. We then apply it to construct the most likely transmission tree during the outbreak in the college campus.ResultsAnalysis of the constructed transmission tree shows that the simultaneous presence of the two influenza viruses increases the infectivity and the transmissibility of A/H1N1 virus but whether it changes the infectivity of A/H3N2 is unclear. The estimation also shows that co-transmission of both subtypes from co-infection is low and therefore co-infection cannot be sustained on its own.ConclusionsThis study suggests that influenza A viruses within co-infected patients can interact in some ways rather than transmit independently, and this can enhance the spread of influenza A virus infection.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-016-1373-x) contains supplementary material, which is available to authorized users.
Highlights
Co-infection of different influenza A viruses is known to occur but how viruses interact within co-infection remains unknown
Recent development in statistical inference [13, 14] allows us to construct the transmission tree of a single influenza A virus from such a partial contact network. In this short report we extend this inference method to construct the transmission tree that includes two influenza A viruses and their co-infection
We further develop it to a transmission tree during an outbreak that involves with two viruses of similar epidemiological characteristics
Summary
For a fully traced transmission tree (i.e., the information of the infector v and time of symptom onset t are collected), the infector v(i) for each case i (except the index case) and the duration between symptom onset of case i and symptom onset of its infector v(i): ti-tv(i) should be known From these it is straightforward to estimate the generation interval distribution and transmissibility of infection. A possible transmission tree can be described by pij(v,w,φ;θ), the probability that case j is the infector of case i, given the duration between symptom onset of case i and case j, given the information on the possible infector v and the known contacts w, and given the types φ of infection of both cases. Ethics considerations Data that were used in the analysis of this study were extracted from a previous study [12] and did not require Human Resource Ethics committee approval
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
