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Diseases we term as ‘emerging’ have likely been around for years
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More than 40 years ago, a “new” viral disease emerged called Lassa fever. It was identified when an American missionary nurse arrived in New York and was admitted to Columbia Presbyterian Hospital with a febrile disease that had not responded to antibiotics. Blood specimens from the patient were inoculated into suckling mice, as was the habit of arbovirologists of the day.
Unfortunately, the virus was one that adapts to rodents and results in persistent infection and urinary excretion of the virus. The investigator and his technician were infected from the rodents. The technician died and the investigator was seriously ill but recovered. Thus, Lassa virus was introduced to the world. It was eventually labeled as an “emerging disease.”
Joseph B. McCormick
Nearly a decade later, an outbreak of a deadly disease occurred in the Republic of the Congo and almost simultaneously in southern Sudan. Ebola virus, one of the most notorious of the “emerging” infections, was similarly introduced to the world. It killed 80% of the 320 people infected in the first outbreak in the Congo, and many of those were infected by contaminated injections, which resulted in 100% mortality. In the meantime, the simultaneous but unrelated outbreak in Sudan exposed yet another “emerging” virus, the Sudan strain of Ebola virus. However, neither Lassa nor Ebola were “new.”
Marriage of technology and science
Later in the 1980s, HIV “emerged” and the term “emerging” viruses was coined. Now, in the light of time and improved technology and advanced understanding of human genetics, we now know that none of these viruses are emerging, but rather science and technology has caught up with nature, and we can now detect or diagnose diseases caused by viruses that have in fact been around for thousands of years — if not longer. Furthermore, signature sequences in the DNA of humans suggest that we may have “adapted” to some of these viruses. In the case of Lassa virus, the presence of persistent Lassa virus in a widespread rodent host, Mastomys natalensis, and the identification of a human gene in the Yoruba population, who reside in the area of West Africa endemic for Lassa virus, that contains sequences that directly affect the receptor for Lassa virus, strongly suggest longstanding human exposure.
Beyond the scientific interest, however, medical professionals need to be aware of the existence of these infections because they occur at all ages and can be transmitted from person-to-person, and modern transport can move someone from an endemic area to another part of the globe in less than an incubation period. Such incidents have occurred, and the tremendous increase in the global population and global travel further increase the probability of such occurrences.
Joseph B. McCormick, MD, led the first HIV investigation in Africa and is the investigator who isolated the oldest HIV strain. His experiences were recounted in the book, “Level 4: Virus Hunters of the CDC,” which he co-authored with Susan Fisher-Hoch, MD.
Source: McCormick JB
Thus, a febrile illness that is not accompanied by a set of signs and symptoms that point to a known likely cause should elicit two questions: 1) has the patient traveled recently, and if so, to where; and 2) has the patient been in contact with anyone who is ill with a fever and has traveled outside the US? These questions should be part of any inquiry into a fever of unclear origin. For example, a patient presented to a hospital in a Chicago suburb some 20 years ago, was in a coma with a fever and hemorrhage and edema of the neck and face — a classical presentation of severe Lassa fever. However, the patient, who was a naturalized American of Nigerian descent, had seen three physicians over the course of about 10 days, and no one asked about travel.
He had returned from the funeral of his mother in Nigeria a week before the onset of his illness, and it turns out she may have died of Lassa fever because there was cluster of Lassa fever cases associated with the funeral, and the Chicago area resident was one of them. He died before ribavirin treatment could be provided, which has been shown to be effective when given early in the course of illness. This is a case in point of the importance of being suspicious of an exotic infection and asking the relevant questions to identify the possible source.
Vigilance needed
So the great increase in population and the increase in travel to previously less accessible areas where endemic viruses such as Lassa and Ebola occur raise the possibility that these perhaps not so recently emergent viruses can arrive at the doorstep of any physician, and therefore every physician needs to be vigilant.
References:
Baron R. WHO Bulletin. 1983;61:997-1003.
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Disclosure: McCormick reports no relevant financial disclosures.