Harvard Medical School researchers analyzed blood and saliva records from over 917,000 people to uncover how common viruses persist without causing disease. The study measured viral DNA load, an indicator of which viruses are present and how well the immune system is fighting them.
The team identified 82 specific locations in the human genome associated with viral DNA load, many within the Major Histocompatibility Complex, a key immune control center. Viral prevalence varied by age and sex; the Epstein-Barr virus load increased with age and was higher in winter, while herpes virus HHV-7 declined from middle age.
Using statistical genetics, researchers found a high viral load for Epstein-Barr virus is a direct risk factor for developing Hodgkin's lymphoma later in life. However, the link between EBV and multiple sclerosis appears dependent on immune response, not viral quantity. Non-genetic factors like smoking also influenced viral DNA loads, with most viruses being more prevalent in men.
The research, focusing on DNA viruses, suggests antivirals could potentially reduce Hodgkin's lymphoma risk. Three anelloviruses were found in 80-90 percent of the population, though their disease relationship remains unclear.