Looks like not all viruses are equal so the IgG vs IgM issue is different.
Based on the info below, I don't think it's possible to know if an HSV-1 or HSV-2 infection is old or new. But that's for two reasons - one is that we have all likely been exposed at a young age and the IgMs (that appear after initially contracting the virus) don't stay around very long.
To answer your question in your 2nd post, Yes, I believe that the only long-term antibodies are going to be IgG. And yes, I think a high IgG volume of titers indicates an active viral load. A low IgG response could indicate a dormant virus.
In answer to your other questions about
EBV, CMV - below is more info.
Here is a good excerpt I found on HSV-1 & 2 IgG and IgM
"IgG appears soon after infection and stays in the blood for life. IgM is actually the first antibody that appears after infection, but it may disappear thereafter.
IgM tests are not recommended because of three serious problems:
1. Many assume that if a test discovers IgM, they have recently acquired herpes. However, research shows that IgM can reappear in blood tests in up to a third of people during recurrences, while it will be negative in up to half of persons who recently acquired herpes but have culture-document first episodes.
Therefore, IgM tests can lead to deceptive test results, as well as false assumptions about
how and when a person actually acquired HSV. For this reason, we do not recommend using blood tests as a way to determine how long a person has had herpes. Unfortunately, most people who are diagnosed will not be able to determine how long they have had the infection.
2. In addition, IgM tests cannot accurately distinguish between HSV-1 and HSV-2 antibodies, and thus very easily provide a false positive result for HSV-2. This is important in that most of the adult population in the U.S. already has antibodies to HSV-1, the primary cause of oral herpes. A person who only has HSV-1 may receive a false positive for HSV-2.
3. IgM tests sometimes cross-react with other viruses in the same family, such as varicella zoster virus (VZV) which causes chickenpox or cytomegalovirus (CMV) which causes mono, meaning that positive results may be misleading.
The accurate herpes blood tests detect IgG antibodies. Unlike IgM, IgG antibodies can be accurately broken down to either HSV-1 or HSV-2. A recent study corroborates this finding: labs that used non-gG-based tests for herpes had high false-positive rates for HSV-2 antibodies (14-88% saying the blood sample was positive for HSV-2) in samples that were actually only positive for HSV-1 antibodies. But 100% of the labs using gG-based tests accurately reported that the blood sample was negative for HSV-2.
The challenge here is that the time it takes for IgG antibodies to reach detectable levels can vary from person to person. For one person, it could take just a few weeks, while it could ta ke a few months for another. So even with the accurate tests, a person could receive a false negative if the test is taken too soon after contracting the virus. For the most accurate test result, it is recommended to wait 12 – 16 weeks from the last possible date of exposure before getting an accurate, type-specific blood test in order to allow enough time for antibodies to reach detectable levels.www.ashasexualhealth.org/stdsstis/herpes/herpes-testing/
An excerpt on HHV-6 (CMV) IgG vs IgM
In a primary infection, which typically occurs before the age of two, IgG antibody levels increase four-fold within several weeks. Most pediatricians test for IgM antibodies to confirm a case of HHV-6 associated roseola or febrile seizures. The IgM antibodies appear within a few weeks and can be detected for several months. A fourfold rise in IgG titers or the presence of IgM antibodies are considered proof of active infection. The HHV-6 IgM antibodies are typically produced only with the primary infection, and not in subsequent reactivations. For this reason, the HHV-6 IgM test is not very useful for adults. Many physicians believe incorrectly that an adult with no IgM antibodies means that the infection must not be active.
Elevated IgG antibody levels can suggest, but not prove active, chronic infection. In a 1996 study of HHV-6 in CFS patients, 89% of the patients with IgG titers of 1:320 and above were found to have active infections by culture (Wagner, Journal of Chronic Fatigue Syndrome). Stanford infectious disease specialist Jose Montoya believes that the best evidence of smoldering central nervous system (CNS) infection is the IgG antibody to the virus, and not the virus itself. In a pilot study, he found that when patients with high titers of HHV-6 IgG (1:320, 1:640 or higher) and EBV are treated with a potent antiviral; their titers fall substantially along with a significant improvement in symptoms.
Elevated IgG Antibodies to HHV-6 cannot indicate with certainty that the infection is active, but high titers support a clinical diagnosis. Similarly, elevated EBV VCA (late antibody) titers also cannot indicate with certainty that an infection is active. However, EBV Early Antigen (EA) antibodies disappear rapidly after an infection is over, so elevated EBV EA antibodies do predict active infection.
Individuals vary in the way they respond to virus: some may not be able to generate antibodies due to a weak immune response. Others may generate large numbers of antibodies to many pathogens, and some healthy individuals have high titers of HHV-6 IgG antibodies.
So looking at elevated antibodies to determine active infection is far from a perfect measure. Montoya is currently conducting a placebo controlled trial of Valcyte in symptomatic patients with elevated antibodies to HHV-6 & EBV. If these patients show a dramatic drop in antibody titers and an improvement in symptoms in response to Valcyte treatment, he will demonstrate conclusively that elevated IgG titers can be a sign of active infection and could be a reliable biomarker for monitoring patients.
The link has more info about
other testing methodologies too:hhv-6foundation.org/research/hhv-6-testing
Let me know if this is still confusing.