Everyone has viruses
New article by "The Scientist" confirms that everyone has viruses and that they are mostly non-problematic till the carrier gets sick or immune-compromised. I've always believed that even healthy people benefit from blood electrification because it lowers the burden on the immune system by lowering viral count. Less immune burden equates to more energy and less sickness.
Viruses of the Human Body
In recent years, great leaps in genomic sciences have allowed researchers to detect viruses living in and on the human body—collectively called the human virome. Recent genomic explorations of human samples have revealed dozens of previously unrecognized viruses resident in our gut, lung, skin, and blood. Some of these newly identified viruses may underlie mysterious, unexplained diseases, but it is also possible that some of these viruses are harmless in most people, most of the time.
A few years ago, only two polyomaviruses were known to infect humans. Using metagenomics approaches, researchers have identified 13 known human polyomavirus strains, and have linked some of these with diseases ranging from neurological or kidney damage in immunosuppressed transplant and AIDS patients to skin cancers.(1) Most of these polyomaviruses infect a majority of people during childhood and are then silently carried until a weakened immune system unleashes them to wreak havoc.
Such occasional pathogenicity is typical of viral families found in humans. For example, some human papillomaviruses are found on the skin of most healthy adults and go unnoticed,(2) while a few specific papillomaviruses can induce cervical or anal cancers (now preventable by early vaccination). Similarly, herpes viruses are nearly universal infections in adults, where they set up lifelong, symptom-free residence in neurons or cells of the immune system. Later in life or following immunosuppression, latent herpes viruses can reactivate and induce diseases ranging from cold sores to meningitis, lymphomas, or Kaposi’s sarcoma.
A rarely studied group of viruses called anelloviruses may claim the prize as the most common human viral infection; they can be detected in the blood of almost 100 percent of adults.(3) Anelloviruses are transmitted very soon after birth and multiple strains can establish persistent viremia in the same person. Because of their level of genetic diversity (the highest of any viral family) anelloviruses may infect different tissues with different consequences. And as with papillomaviruses, it is conceivable that only a subset of anelloviruses may turn pathogenic.
Whether such common and persistent viruses affect health is still being sorted out. A frequent consequence of chronic and acute viral infection is immune overstimulation. The increasing concentration of anelloviruses seen in immune-suppressed individuals indicates that anelloviruses remain under immunological control and may therefore result in low-level chronic inflammation, known to result in myriad health problems.
Beside the nearly universal blood-borne viruses described above, a cornucopia of other recently discovered viruses can be detected in respiratory and fecal samples of healthy persons, particularly children. These viruses include a growing number of astroviruses, parvoviruses, picornaviruses, picobirnaviruses, and others whose roles in health and disease also remain largely unknown.
This flood of new information regarding our virome indicates that, even when in perfect health, we are chronically infected by several types of viruses and often transiently infected by yet others. The perception that every human virus causes disease is therefore yielding to a much more complex biological reality.
IS IT A PATHOGEN?
To assess pathogenicity, researchers still rely on the four postulates for pathogenicity established by German physician and microbiologist Robert Koch in the late 1800s: 1) the agent is found in only those people with the disease, 2) the agent can be isolated from diseased individuals, 3) inoculation with the agent causes disease, and 4) the virus can be reisolated from the inoculated individuals.
But satisfying these postulates for human viruses is a tall order. Firstly, many viruses cannot be purified and grown in culture. Moreover, because human inoculations are unethical, researchers need to use animal models, such as rhesus macaques and mice, because many human viruses only infect humans.
Alternatively, researchers can try to demonstrate that the virus is found replicating at the site of pathology: the liver for hepatitis, for example, or the brain for encephalitis. Detecting only a single virus in diseased tissues, a feat made possible by deep sequencing, can also provide supporting evidence for its culpability. But this approach also has its limitations, as human necropsies (analysis after death) are costly and thus rarely performed, often leaving blood as the only available tissue type for study. In such cases, measuring the emergence of antibody response to a new virus to show that the timing of the viral infection corresponds to the onset of the immune response can help identify a likely culprit.
Case control studies that compare virus detection rates in patients or animals with similar symptoms versus healthy controls can provide powerful evidence of virus-disease association. Such studies control for age, geographic origin, gender, socio-economic status, and even time of year of sample collection, leaving only the disease state to differentiate the two groups. Most viruses are neither consistently pathogenic nor always harmless, but rather can result in different outcomes depending on the health and immunological status of their hosts. The less pathogenic a virus is the lower the percentage of infected people who become sick and the larger such case-control studies need to be to detect a difference between the groups.
Viruses in our DNA
In addition to the viruses that can infect us, humans (and all other vertebrates) have traces of past viral infections integrated into our very own genomes. About 8 percent of the human genome consists of retroviral DNA sequences that have inserted themselves into the human germline, where some of their functions have been adopted to serve essential functions for their host’s survival and development.(12) Clearly, our very long evolutionary history in a bacteria and virus rich environment has driven human adaptation to many such infections, from the cellular level domestication of retroviral genes and hyperreactive immune systems to the cultural: adaptations intended to reduce the burden of infectious diseases.
1. J.A. DeCaprio, R.L. Garcea, “A cornucopia of human polyomaviruses,” Nat Rev Microbiol, 11:264-76, 2013.
2. V. Foulongne et al., “Human skin microbiota: High diversity of DNA viruses identified on the human skin by high throughput sequencing,” PLOS ONE, 7:e38499, 2012.
3. S. Spandole et al., “Human anelloviruses: An update of molecular, epidemiological and clinical aspects,” Arch Virol, 160(4):893-908, 2015.
12. D.J. Griffiths, “Endogenous retroviruses in the human genome sequence,” Genome Biol, 2:reviews1017.1, 2001.