The issue in those days, in the 1970s and 80s, was that the UK ME/CFS researchers were unsure what the high antibody titers to coxsackievirus B actually meant.
Was there a chronic enterovirus infection in ME/CFS patients, or are the high titers just due to dysfunction of the immune response, creating a high titer, but where there is no ongoing infection?
But then in the 1990s when PCR became available, the UK researchers were able to show that the muscles of ME/CFS patients contain enterovirus RNA, thus indicating a chronic infection of the muscles.
Though when researchers in the US tried to replicate the UK research, they did not look at the muscle tissues, but rather performed PCR testing on blood samples from ME/CFS patients, where they got a negative result.
This is why historically, the US discounted the enterovirus theory of ME/CFS, because of these negative PCR blood tests. The US then focused on herpesviruses in ME/CFS (which is a good thing, because herpesviruses are also linked to ME/CFS). Even today most ME/CFS doctors in the US still focus more on herpesviruses than enteroviruses, with the exception of Dr Chia.
But we now know why these PCR blood tests for enterovirus are negative in ME/CFS patients, even though patients have high antibody titers to enterovirus and have a positive PCR on muscle tissue tests: it is because the enterovirus infections in the tissues do not produce any new viral particles (or only a very small amount of viral particles). If very few new viral particles are being produced, then you will not find much virus floating around in the blood, and thus a blood PCR test will often be negative.
These enterovirus infections that ME/CFS patients have in their tissues are non-cytolytic infections, which do not produce new viral particles. That fact really solves the mystery of enteroviral testing in ME/CFS.
It was Professor Steven Tracy et al at the University of Nebraska who I believe discovered these enterovirus non-cytolytic infections.