The ticks which transmit Lyme can also transmit a number of other bacterial and viral infections. The immune suppression caused by Lyme can also cause re-activation of viruses or allow opportunistic infections to take hold, as in HIV/AIDS.

The main co-infections reported are Bartonella, Babesia, Mycoplasma, Chlamydia Pneumoniae and Erlichia/Anaplasma. The main re-activated viruses seen are Epstein-Barr and Coxsackie.

A chart summarising the symptoms seen in these infections and others can be found here. As with Lyme, many doctors prefer a clinical diagnosis of these co-infections, but the two main international testing labs for Lyme do also test for these.