A Canadian study showed [9] that detection of IgM presented diagnostic difficulties in a highly vaccinated population, as a demonstrable increase in IgM levels following infection was often delayed or altogether absent in such individuals; detection of mumps virus by reverse-transcription polymerase chain reaction (RT-PCR) was considered the gold standard for mumps diagnosis, but the success of detecting the virus depended on the technique used to collect and transport specimens as well as on the time of collection. Here, CD40LG is linked to infection.