Hello Lauren,

I am not a dahlia expert, but it appears to me that your bulb does have a virus.  You see the newly emerged  leaves with what is called, 'vein clearing' evident - or yellowing chlorotic veins There is also a necrotic brown lesion on one of the leaves as well. 

Unfortunately, dahlias are known to suffer from viruses and there is nothing that can eradicate them, so it is best to dispose of the infected bulb. The virus is spread from an infected plant to a nearby healthy plant via a cut or wound by sapping sucking aphids. 

It https://dahlia.org/wp-content/uploads/2018/01/ADS-DMV_Symptoms_Slides.pdf - this site is one that  shows you various dahlia leaf viruses. 

As a best practice, it is most important with dahlias to use disinfected tools at all times to prevent the spread of the virus from tuber to tuber. 

Kathleen