Nov 14 2008
Human Herpes Virus
Human Herpes Virus
The human herpesviruses (HHV) are a very large family of DNA viruses, many of cause disease in humans. Following the primary infection, all herpesviruses establish a LATENT INFECTION in the host. At a later time, the virus may reactivate and frequently, but not always, is associated with further disease.
(not a true story)
It was April, and the freshness of spring had just begun to wash away the gloom of winter. But this spring brought 25-year-old Melissa to the ER with shaking chills, night sweats, and vomiting-the flu. Her prescription was simple: plenty of rest, plenty of fluids.
The plan worked until she became angry and mean-spirited, and lost interest in her personal appearance. “Just the flu,” her doctor said to her anxious husband. Then she stopped eating, and seizures started to occur. Again the ER physician said it was just the flu, and Melissa was sent home.
Within days, she was almost catatonic, unable to do little more than drool. This time her husband, in an act of devotion that saved Melissa’s life, refused to leave the emergency room until the attending physician agreed to admit her.
Dr. MacKenzie was on call. He started by reviewing the lab data. The only hint of infection was her elevated white-blood-cell count. Where was the infection? Blood and urine cultures were negative, and her chest X ray didn’t show any pneumonia. The clinical presentation suggested a central nervous system disease. A lumbar puncture showed spinal fluid consistent with a viral infection. But another detail about the spinal-fluid analysis caught the physician’s attention - red blood cells, a sign of bleeding in the brain. Perhaps she had encephalitis. Many viruses can infect the brain, but he knew of only one with that signature: herpes simplex.
Herpes simplex viruses type 1 and type 2 tend to infect mucous membranes and the central nervous system. HSV-1 causes cold sores and spreads through contact with virus-laden saliva or sores. People usually get infected in childhood or adolescence. Sometimes there are no symptoms, but more often people have cold sores, or “fever blisters,” in or around the mouth. After the first infection the virus lies latent in the trigeminal ganglia, a structure in the base of the brain that gives rise to the trigemincal nerve, which predominantly provides sensation to the face. For reasons that are not clear, the virus can reactivate years later and travel along the trigeminal nerve to the meninges, the coverings of the brain and spinal cord, at the base of the brain. From there it can launch an attack on its preferred target: the temporal lobes, brain regions just above each ear that help carry out the complex functions of hearing, learning, memory, and emotion.
Untreated herpes encephalitis can be fatal in up to 70 percent of cases. Malaise, fever, and headache herald its onset, often quickly followed by behavioral abnormalities, seizures, olfactory hallucinations, and bizarre or psychotic behavior - all symptoms of disease in the temporal lobes.
Fortunately, effective antiviral therapy is available, and early treatment reduces mortality to 30 percent. But making the diagnosis promptly is vital. And even with treatment, survivors of herpes encephalitis are almost never neurologically normal and will often experience amnesia, seizures, and a loss of smell.
When Dr. MacKenzie first examined Melissa, she was comatose. An electroencephalogram showed slowing of the normally brisk electrical activity of the brain. That finding fit with her comatose condition, but it is not typical of the waveforms often seen in herpes encephalitis.
Still, Melissa was dying and something had to be done now. Dr. MacKenzie followed his instinct and treated her for herpes encephalitis with acyclovir, and antivial drug.
His gut instinct paid off. Melissa eventually recovered, but her return home was like stepping onto the set of a movie she’d never seen. She couldn’t find the guest bedroom, and she didn’t remember she had been taking tennis lesson. She didn’t even recognized faces. Pictures of high school friends were the faces of strangers. She could identify a face as a face, its parts, and even certain emotions, but she was unable to identify a particular face as belonging to a specific person. She could not even recognize her own face in the mirror, although she recognized that it was a face.
Still, Melissa didn’t lose her knowledge of people’s identities. She just couldn’t count on using facial recognition to make identifications. Because humans are remarkably adaptive, patients like Melissa can often be taught how to compensate. Over time, Melissa learned to recognize people by context, such as where she last saw a person and what he or she was wearing. Dr. MacKenzie saw this firsthand when he met her for a follow-up visit. Only when they were seated in the customary positions in his office did he see a glimmer of recognition flash across her face.
After several months of rehabilitation, Melissa was able to return to teaching. She now leads a near-normal life. During her last visit with Dr. MacKenzie, he said he was pleased at her recovery. With a twinkle in her eye, and as if to make light of it, she smiled slyly and said, “Doc, it’s just a matter of recognition.”
-Dr. Pommerville-
