Machupo

MACHUPO VIRUS

As mankind has expanded in the twentieth century it has encountered some viruses that cause highly lethal hemorrhagic fevers. The threat posed by these new found viruses has prompted the development of new techniques of study and treatment. A pioneer in the study of these deadly viruses is Dr. Karl Johnson, who discovered the Machupo virus while working as a virologist for the Centers for Disease Control. The Machupo virus causes a mortality rate of about 30%. The path toward the discovery of the Machupo virus began in 1962 when Karl Johnson was at the Middle America Research Unit in Panama and fellow doctor, Ron MacKenzie, invited him to travel to Bolivia. The project was intended to do a nutritional analysis of the village people, but turned out to be much more. In order for the nutritional study to begin the two needed to receive permission from the Bolivian Minister of Health. The Minister of Health granted permission to do a the nutritional analysis, but only after the two doctors had studied a
strange disease that was killing many of the villagers in Magdalena. The doctors were happy to agree, asthey found it to be more interesting than conducting a study on nutrition.

Upon landing in the small village of Magdelena they immediately visited the hospital, where they found ten patients suffering the symptoms of a hemorrhagic fever. Because of the severity of the situation in Magdelena the scientists returned to the United States to obtain more funding and a larger research team. A new team of researchers was sent in March of 1963. It included Merl Kuns of the University of Wisconsin-Madison. He was selected as the ecologist to accompany Ron MacKenzie. They concluded that the outbreak was more severe than expected and determined that the location of the outbreak was actually in San Jouquin. In May of 1963, Karl Johnson and new experimental equipment joined the team in San Jouquin. The new equipment consisted of a coffin size glass box that cycled air out through filters and had a set of latex gloves built in. The boxes stored mutant immuno-deficient mice used for quickly testing viruses. This assembly would be sized down and improved to become the future of studying dangerous viruses.

The research began favorably, but was cut short when MacKenzie and Johnson became strangely infected. The two doctors traveled back to Panama where an army doctor familiar with hemorrhagic fevers caused by the Hantaan virus was able to save them. The doctor used similar treatment used on Hantaan suffers in the Korean war. This involved maintaining electrolyte, vitamin, and other fluid levels. Kuns continued to collect animal samples in hopes of finding the host while his colleagues were hospitalized. Johnson and MacKenzie believed they had become immune to Machupo and finally returned to complete the study. Their own infection threw new light on the research. The virus was ultimately found in the food supply, which was the only common link the doctors shared with the people. The host animal was identified as a common mouse that occupied most homes and urinated in grain baskets. Transmission of viruses through urine was proved possible in animal tests. It was concluded that mouse traps proved to be the most effective preventative measure in avoiding the Machupo virus. Ecological explanation of the event was that it was a simple result of farming. New farmland allowed the common mouse, Calomys Calosus, that carried the virus to increase in numbers as food increased and it’s competitor, a larger mouse, became less successful in the new environment. Perhaps it’s fitting irony that human expansion was the cause of the Machupo outbreak. This ecological cause was something that scientists would continue to see as a cause of virus outbreaks. Unfortunately, in the San Jouquin outbreak, Merl Kuns felt that all hosts were not identified and the research was never completed, but funding ended and the team returned home.

After the outbreak ended the total number of people infected was estimated at 470 and resulted in 192 deaths between 1959 and 1965. No reported outbreaks of Machupo have been reported until 1994 when there was a presumed 10 cases resulting in 6 deaths. The outbreak occurred in the Magdelena area mostly within one extended family. Results found by research teams found no evidence of the virus in 9 Calomys Calosus, nor in any of the other 73 rodents captured in trap. This result supports Kuns assertion that all hosts were not found and proves that not all is known about Machupo. The initial study did help to develop new tactics and treatments that would be followed in other viral outbreaks. The outbreak helped educate future scientists to stay extremely cautious and begin searches with obvious causes. It also allowed for continued improvement of treatment for suffers of hemorrhagic fevers. Another aspect of the outbreak was that it gave prestige to Karl Johnson, who would go on to make a successful career of working with lethal viruses.

In lab studies, samples of the Machupo virus, also known as Bolivian Hemorrhagic Fever, identify it as part of the Genus Arenavirus and Family Arenaviridae. It has a structure that relates it to the Tacaribe complex. This fact helps further categorize it as a new world virus, meaning it is native to the Americas. As a member of the genus Arenavirus it contains it’s genetic information in the form of single stranded negative sense RNA. This structure allows for a mechanism where the negative sense RNA is translated by the host to produce viral RNA polymerase which produces positive strands of RNA. These positive sense strands have the codes for the necessary proteins and additional negative sense strands of RNA that are the building blocks of the virus. The entire genome of Machupo has been mapped using PCR, Polymerase Chain Reaction, and can now be treated using ribavirin, a antiviral drug. Success varies on when the drug is administered. The sooner the drug is administered the better the chances of survival and a quick recovery.

The Machupo virus remains a risk, but is limited in danger by several circumstances. The virus is dangerous, because it a airborne infectent and is transmitted through bodily fluids or contact with the virus. Yet, it can easily by prevented by mouse traps and other mechanisms of eradication that help control host populations. Further limiting its potential is the fact that the virus is located deep in the Bolivian jungle which acts as a natural barrier preventing spread due to slow travel conditions. Combined with the conventional knowledge about its structure, Machupo may be brushed aside as a immediate threat. Yet, it still remains a very lethal threat which any person could become a victim if the virus escaped its current constraints of the jungle.