LEARNING ABOUT VIRUSES

VIRUS OVERVIEW AND UPDATE

 

Severe Acute Respiratory Syndrome (SARS)

There is a new strain of the potentially deadly virus related to SARS. The initial fear was we’d be facing an aggressive form like the outbreak in China that killed one in ten victims and infected about 8,000. The World Health Organization reports this new form is not as easily spread from person to person. Like the SARS outbreak which began in China in 2002, it is related to a common cold virus of the coronavirus family. Only one person has died. One person is critically ill. Both are from the Middle East where this new form was first identified.

Influenza A (H3N2v) Variant Virus Outbreaks

The H1N1 virus, found in pigs (2010) and humans (2011) has now surface as a new variant which has infected humans resulting in one death. The variant is transmitted from pigs to humans by droplet contact. Most infected developed only mild symptoms. Any one who is under age 5, over 65, or are pregnant, have diabetes, heart disease or weakened immune systems are at high risk of serious complications. They must have no contact with pigs. There is no risk with eating cooked pork. The seasonal flu vaccine will not protect you from this disease. See a doctor early if you suspect this infection as antiviral drugs may help.  http://www.cdc.gov/flu/swineflu/h3n2v-outbreak.htm

Viruses in Health and Disease

We have all had numerous viral illnesses with little evidence of persistence. Yet, after mapping the human genome, scientists found viruses incorporated into human genes. In fact, 8% of the human genome consists of endogenous (embedded segments) of virus sequences we pass on to our offspring. Many of these are retroviruses, based on RNA. To be functional, RNA viruses must insert themselves into a DNA-based genome which contains reverse transcriptase. The enzyme allows the RNA virus to reproduce itself using the cell’s machinery.

We have known for years that cancers arise from viruses. The Human T-cell Lymphotropic Virus (HTLV) was the first human retrovirus discovered. This virus affects T lymphocytes, white cells responsible for fighting infection. HTLV-1 and HTLV-2 are involved in numerous disease processes including leukemia, lymphoma, skin and neurologic disorders.

The Human Papilloma Virus (HPV) causes a variety of aggressive cancers: cervical, penile, oral and throat. Prevention of HPV-based cancers is now possible with an immunization. (HPV Vaccination) For guidelines: www.cdc.gov/vaccines/vpd-vac/hpv/

 

A recent discovery by researchers at the University of Texas broadens understanding of the viruses embedded in our genes. They found human genomes and those of other mammals contain Bornavirus DNA. This is an RNA virus which activates viral factories within the cell nucleus establishing persistent infection, and has been passed in mammals throughout evolution. Researchers looked at more than 200 genomes and found Bornavirus sequences in them. Why do you care?

First of all, Bornavirus infects a large number of animals internationally from birds to primates. It causes a severe and usually fatal form of encephalitis with striking behavior changes in horses, but is also seen in cattle, sheep, cats and canines. Changes in horses include: staggering, agitation and depressed behavior. Transmitted by contact with secretions, there is an incubation period from weeks to months.

Viral infections caused by influenza, cytomegalovirus (CMV) and herpes simplex virus (HSV) may be involved with psychiatric disorders but no clear causation has been reported. Bornavirus antibodies and viral RNA have been found in humans with psychiatric disorders but there is no proven direct causal link between Bornavirus infection and mental problems. Genetic and environmental factors both interact in the expression of psychiatric illness including schizophrenia and mood disorders. Research is ongoing and is a field to watch.

Information on this virus, its diagnosis and correlation with evidence for possible infection in humans causing mental disorders is discussed in detail in the following source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC164222/ from Clinical Microbiology Reviews.

There is much we do not know about how latent viruses may affect our health. Maybe they will never surface and will lie dormant in our genes over a lifetime. Many people are all too aware of Varicella Zoster Virus. This one lies dormant after having chicken pox as a child. Anyone who has had chicken pox and recovered may develop this painful blistering skin rash that follows nerves along one side of the body. One out of three people develop shingles. The best treatment is prevention and an immunization is available, even at local pharmacies. There are medications that help and you should see a doctor if you develop shingles. Zostavax® immunization is recommended by the CDC for those over age 60.  Guidelines at the CDC:

http://www.cdc.gov/vaccines/vpd-vac/shingles/vacc-need-know.htm#get-vaccine

Studies show viruses change the way genes turn on and off in embryonic stem cells. As more research information surfaces, studies using new molecular mechanisms to turn cell functions on and off are designed. Cancer treatment studies are now targeting the on-off switches which could stop rapid growth of abnormal cells and halt cancer growth.

Betty Kuffel, MD

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