One way of assessing the rate of infections is by looking for antibodies. This underestimates the rate of infection, because infections do not always generate antibodies, and antibodies can be lost during a persistent infection. However, antibodies can be detected in a simple blood test, making them the most useful measure of prevalence.
So what fraction of the population has antibodies to pathogens that produce chronic disease?
One representative study , conducted among Alaskan Eskimos, found that:
- 94% were infected with cytomegalovirus (CMV), 90% with herpes simplex 1 (HSV1), 38% with herpes simplex 2 (HSV2), 80% to H. pylori, and 42% to C. pneumoniae.
- Over 70% had antibodies to at least 3 of the five pathogens tested.
- Seropositivity increased with age: a majority had antibodies to HSV2 and C. pneumoniae by age 45.
Infection rates are similar in other populations. Let’s look just at C. pneumoniae:
- Among Japanese, 59% to 73% have antibodies.  Dr. Naoyuki Miyashita notes that “C. pneumoniae is widely distributed and that nearly everybody is infected with the agent at some time.” 
- Among Finns, the prevalence of antibodies rises sharply through childhood, reaching 70% in 15-19 year olds. In elderly Finnish men, prevalence is 100%. 
- Among Israelis, 31% of children and 74% of adults are antibody-positive. 
- Among Italian schoolchildren, 29% have antibodies, and the prevalence increases steadily with age. 
- In Singapore, antibody prevalence is 75% in men and 65% in women. By age group, it is 46.5% at ages 18-29 and 78.9% above age 40. 
Keeping in mind that C. pneumoniae infections often do not trigger antibody production, it seems certain that by age 40 nearly everyone has been infected.
Likewise there is no avoiding infection with other chronic pathogens. Likely agents include bacteria like Mycoplasma and viruses like cytomegalovirus, Epstein-Barr, and HSV1.
These infections cause few symptoms in the young. Over time, however, pathogens reproduce within the body and increase their numbers. The immune system is gradually overpowered. In the elderly, symptoms of chronic infection become increasingly common.
A thesis of this blog is that most of what we consider “aging” is not a natural degeneration of the human body, but increasing debilitation from chronic infections. Cardiovascular disease, dementia and memory loss, neuropathy and lost balance and falls, “grouchy old man” syndrome, cold intolerance, inflamed and arthritic joints – these are all symptoms of chronic infection.
But this is good news. Through diet, nutrition, and antibiotics, we can cure chronic infections. By doing so, nearly everyone can hope to maintain vitality and good health to a ripe old age – 100, or older.
 Zhu J et al. Prevalence and persistence of antibodies to herpes viruses, Chlamydia pneumoniae and Helicobacter pylori in Alaskan Eskimos: the GOCADAN Study. Clin Microbiol Infect. 2006 Feb;12(2):118-22. http://pmid.us/16441448.
 Miyashita N et al. Seroepidemiology of Chlamydia pneumoniae in Japan between 1991 and 2000. J Clin Pathol. 2002 Feb;55(2):115-7. http://pmid.us/11865005.
 Miyashita N. [Chlamydia pneumoniae infections]. Kekkaku. 2006 Sep;81(9):581-8. http://pmid.us/17037392.
 Tuuminen T et al. Prevalence of Chlamydia pneumoniae and Mycoplasma pneumoniae immunoglobulin G and A antibodies in a healthy Finnish population as analyzed by quantitative enzyme immunoassays. Clin Diagn Lab Immunol. 2000 Sep;7(5):734-8. http://pmid.us/10973446.
 Ben-Yaakov M et al. Prevalence of antibodies to Chlamydia pneumoniae in an Israeli population without clinical evidence of respiratory infection. J Clin Pathol. 2002 May;55(5):355-8. http://pmid.us/11986341.
 Dal Molin G et al. A population based seroepidemiological survey of Chlamydia pneumoniae infections in schoolchildren. J Clin Pathol. 2005 Jun;58(6):617-20. http://pmid.us/15917413.
 Koh WP et al. Seroprevalence of IgG antibodies against Chlamydia pneumoniae in Chinese, Malays and Asian Indians in Singapore. Int J Epidemiol. 2002 Oct;31(5):1001-7. http://pmid.us/12435775.