Germs Chapter 3, The Deadly Viruses

There exist many viruses that are lethal or at best controllable. HIV, rabies, and hemorrhagic fevers all are included in the "deadly viruses".

Rabies is caused by a rhabdovirus. There is a large reservoir of rabies in the animal kingdom. In the US, bats, raccoons, skunks, coyotes and foxes are common sources. Any predator animal and even some large prey animals may harbor rabies. Bites, scratches and even saliva may transmit the virus. Animals who are infected die. The viral inoculation occurs at the site of penetration. The virus travels up the local peripheral nerves and eventually makes its way into the central nervous system ultimately causing encephalitis and death. Infected animal often display abnormal behavior. Aggression and unprovoked attacks may be evident. During the late stages, the infected animal or human has difficulty swallowing. The drooling saliva from this dysphagia gave rise to the term hydrophobia (fear of water) to describe rabies.

Rabies is not universally fatal. There have been a few victims who survived. The Milwaukee protocol arose from the survival of a young woman after she became infected with rabies. The treatment involved a drug induced coma. Ketamine, midazolam and phenobarbital were used to place the patient in a coma. Antiviral medication (ribavirin and amantadine) were given intravenously. The patient has made a remarkable recovery. Other factors may have aided her survival. The bite was in her finger. The strain of the virus may have been weak.

The treatment of rabies involves giving passive immunity by injecting RIG (rabies immune globulin) into the area of the bite and into the large muscles of the buttocks. The amount of RIG is based on the patient's weight. Stimulating active immunity is done by giving rabies vaccine in several doses over the course of a month. This treatment can have painful and even serious medical side effects. If the source animal can be tested and found to not have rabies, the human victim may be spared those many injections.

Don't feed or even approach feral animals. Dogs in the US rarely harbor rabies. Feral cats are a potential source. Be careful and notify animal control as soon as possible.

Viral hemorrhagic fevers include Crimean-Congo, Rift Valley and South American strains. The filoviruses that cause Ebola and Marburg also cause hemorrhagic illnesses. The symptoms include fever, petechiae, mucosal and gastrointestinal bleeding. Severe headaches, hypotension and vomiting and diarrhea occur. The only treatment is supportive care with hydration, blood products and careful monitoring. The mortality rate is high.

Yellow fever, and Dengue are caused by flaviviruses. They cause liver damage, with jaundice being evident (yellowing of the skin and conjuctiva). Black vomitous is often seen in Yellow fever. There is a vaccine available for these diseases and if you are traveling to areas that are endemic for them, you should get the vaccination. Mosquitoes are the carrier for all the hemorrhagic fevers. Use of bed netting and avoidance of mosquitoes are good practices in endemic regions.

As an emergency medicine resident back in the late 70's, I saw a few young men with purple colored skin lesions. The had fevers, weight loss, unusual infections such as pneumocystis pneumonia. The skin lesions were shown by biopsy to be Karposi sarcoma. I had read in my pathology text that this cancer was usually seen in elderly men from the Mediterranean area.

AIDS was the name given to the constellation of diseases caused by HIV. The virus was subsequently identified as a lentivirus. This retrovirus uses RNA as its genetic material. After thirty years of research, no effective vaccine to prevent HIV infection exists. HIV binds to and kills a type of lymphocyte that is involved with human cellular immunity. The infections and cancers that make up AIDS, arise because of the damage to the patient's immune system.

The early history of HIV/AIDS was of horrible, wasting death. Although not curable, HIV/AIDS has become a chronic manageable disease. HAART is highly active antiretroviral therapy. This treatment uses medication that attack the virus in several ways. Nucleoside Reverse Transcriptase and non-Nucleoside Reverse Transcriptase inhibitors interfere with the virus's ability to copy its RNA. Protease, entry, and integrase inhibitors work by other mechanisms to hinder the HIV. The patients are followed with blood tests to monitor their viral load and CD4 lymphocyte counts. These potent medications have significant side effects. They must be taken faithfully. Unfortunately, the incidence of HIV is increasing because of continued unsafe sex practices and IV drug abuse.

HIV exposure from occupational needle sticks or unprotected sexual contact can be treated with PEP (post-exposure prophylaxis). This involves taking anti-retrovirus medication for several weeks. It is effective but the side effects of the medications make it difficult to complete the treatment.

Hepatitis C is caused by a single strand RNA virus. It is spread by contaminated needles or blood exposure. There is a treatment involving pegylated interferon and ribavirin. The treatment doesn't work for all patients and the side effects of the medications may prevent completion of the treatment course. Hepatitis C often leads to cirrhosis and hepatocellular carcinoma many years after the initial infection. The blood supply is no longer a source of this disease. IV drug abuse and occupational exposure to infected blood are the main sources.

I find it humbling that the simplest living organisms (viruses) cause so much human illness. Our overpopulation and encroachment into all environments on this small planet have exposed us to many of these scourges. Knowledge and research are the best chance for our overcoming these diseases. Stay informed, practice safe sex, if you use IV drugs, avail yourself of clean needle exchange programs. When traveling, check with the CDC for advisories concerning diseases in the areas you are visiting.