Ebola Hemorrhagic Fever. One of the most terrifying infectious diseases known to man has once again mysteriously surfaced, this time in the Gulu district of northern Uganda. To date, this outbreak has seen 191 confirmed infections and 68 deaths from this terrible pathogen.

The virus (or one strikingly similar to it) has been the unseen evil in major Hollywood productions (Outbreak, with Dustin Hoffman), books of fiction (Outbreak, without Dustin Hoffman) and even, most famously, a best-selling nonfiction treatment (The Hot Zone), and with good reason. The virus has all the makings of a 21st century horror: It is invisible, lightning quick, mysterious and horrible.

The Ebola virus can be spread through any sort of close physical contact, especially with mucous membranes. This makes family members of infected individuals and medical personnel the most likely to contract the disease. In fact, in specific previous outbreaks, up to a quarter of deaths have come from medical personnel infected by their patients. In the laboratory, Ebola has been shown to be transmittable in aerosol form (i.e. through the air, just as a cold or a flu can be transmitted in a sneeze or a cough) but no human infection has been confirmed to have occurred through air-borne particles.

The monster strikes notoriously quickly. While incubation times have been known to vary from two to 21 days, the Centers for Disease Control and Prevention (CDC) states that death usually comes within one week after infection. Those who succumb to the virus usually have not developed a significant immune response. In other words, it seems that the virus often replicates so quickly that it overwhelms the body before the immune system can even register that an infection has occurred.

Because the virus is not stable in the human population (it cannot co-exist with humans because it ends up killing them so quickly), researchers postulate that the virus resides in a host species normally, and the virus sporadically jumps into humans causing outbreaks in the general population. But this source organism has not been found. Although the virus has been exposed to a host of possible host organisms, only very superficial evidence for a possible carrier has been unearthed. Today the environmental source of Ebola is as mysterious as it was in 1976 when the first cases were reported in Zaire. Different strains of the virus have different mortality rates, ranging from about 90 percent for Ebola-Zaire (the viruses are named after the places they are first discovered) to about 55 percent for Ebola-Sudan. Researchers still do not have a good explanation why some people survive infection and others do not.

So how do you tell if you have contracted the dread virus? Well, the rest of this column goes out to all the hypochondriacs out there. Quite perniciously, the first symptoms of the infection in the early stages are similar to those of the common flu. The CDC warns that most stricken with Ebola display high fever, headache, muscle aches, stomach pain, fatigue and diarrhea, and some patients also complain of sore throat, hiccups, rash and red itchy eyes within a few days post-infection. Of course, these symptoms could easily be confused with numerous every-day maladies (from the common flu to pre-midterm stresses), which is what makes Ebola so difficult to diagnose and quarantine early in an outbreak. Less common are early symptoms that belie a major malady, such as vomiting blood and bloody diarrhea.

Quickly after the onset of these initial, mostly benign symptoms, more serious symptoms such as chest pain and shock ensue, and some patients become blind or begin to bleed profusely. This bleeding is caused by the breakdown of membranous tissues that separate different parts of the body from others. As these cells become infected and release their viral loads, the patients' organs effectively liquefy. Membranes that separate the patient from the outside world also breakdown, releasing this internal viral slurry. In effect, the patient becomes a human virus bomb.

But the horror does not even stop with the death of the patient. In fact, infected persons are most contagious just before and just after death, and many cases of Ebola have been documented to come from contact with the dead during burial procedures. The deadly hand of Ebola reaches out even from the grave.