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Tropical countries offer what is difficult to access in a place of residence, which is attractive and gives a substitute for a biblical paradise. But let’s not forget the well-known saying that “every medal has two sides.” Viruses can pose a threat – tropical pathogenic microorganisms that can cause serious diseases.
For most of us, the exotic regions of our globe, especially its tropical regions, are associated with the vestibule of Eden. A feast of colors, an abundance of unknown fauna and flora, a climate reminiscent of a European summer lasting all year round, tempting tastes and smells, in a word, attractive diversity. Nowadays, if only finances allow, anyone can move to a selected region of the Earth within a dozen or so hours and taste the exotic first-hand. Indeed, tropical countries offer what is difficult to access in a place of residence, which is attractive and gives a substitute for a biblical paradise. But let’s not forget the well-known saying that “every medal has two sides.” Let us omit here the problems and hardships of everyday life experienced by the inhabitants of “earthly paradises” and focus on the problem of tropical viruses.
Ebola virus and Marburg virus – infection
Just as tropical countries are exotic, so are tropical viruses. Exoticism is, by definition, nothing more than difference, originality in relation to what we usually experience on a daily basis. Likewise, there are well-known infectious diseases and microorganisms because of where we live, and there are exotic (usually tropical) pathogenic microorganisms.
The popularity of global travel favors the rapid spread of exotic viruses around the world. New etiological factors of infections (i.e. new pathogenic microorganisms previously unknown to medicine) usually appeared in tropical areas of Africa or South America. This phenomenon is related to exploration, i.e. human interference in virgin ecosystems so far untouched by a human foot. Some scientists believe that hitherto unknown viruses that kill humans exist in the depths of the Amazonian forests. This was the case, for example, with the Marburg virus (filovirus) – named after the town in Germany where the virus first appeared – which caused an infection and an epidemic that began in a laboratory where exotic monkeys carrying this pathogen were found. Several people died. Another example is the Ebola virus (filovirus), which was first officially identified in Zaire in 1976 near the Ebola River (hence the name of the virus); the reservoir was probably monkeys. Ebola causes a higher mortality rate than the Marburg virus (Marburg disease).
Viral hemorrhagic fever – symptoms
Both the viruses mentioned above – Marburg and Ebola – cause symptoms of hemorrhagic diathesis, which gives rise to a general range of diseases caused by them as viral hemorrhagic fever. The initial symptoms of infection are similar to flu infection (this is how most viral infections manifest themselves, regardless of the type of virus), that is: headaches, high fever, general weakness and breakdown, diarrhea and vomiting – this condition lasts for about a week. Then symptoms of hemorrhagic diathesis develop, i.e. a tendency to numerous minor and major bleeding, mainly from the mucous membranes of the oral cavity, conjunctiva, nose, gastrointestinal tract, and lungs caused by a reduction in the level of platelets (thrombocytopenia). Mortality is high and can be 25-90%. Death occurs within a dozen or so days, usually as a result of shock caused by blood loss. These viruses have an affinity for many organs in the human body, but cause the greatest damage to the liver and spleen. As infection is spread through the bloodstream, adequate personal protection of medical personnel is essential. So far, we do not have any vaccines or effective drugs against these microorganisms.
In addition to the Marburg and Ebola viruses mentioned, others are known that can also cause symptoms of hemorrhagic fever. These viruses are classified as Arenaviruses and are of a different family from the Filoviruses described above. One of them is Lassa virus, the reservoir of which is a rat native to West Africa. Infection occurs as a result of contact with rat faeces, which can take place, for example, during agricultural work in the areas where this rodent lives. While working, agricultural machinery can spray an aerosol of soil manure or even the blood of rats that entered the combine during harvesting. The aerosol particles are inhaled and deposited in the bronchi. Symptoms are similar to those of Marburg or Ebola viruses. Bolivian hemorrhagic fever caused by thromboembolism can also be mentioned sand virus Machupo. Again, the disease spreads through the excreta of rodents.
Other reported hemorrhagic fever are Argentine hemorrhagic fever (Junin virus), Rift valley fever, Congo fever, and renal failure hemorrhagic fever (hantavirus).
The threat of zoonoses
The listed diseases are zoonoses, or zoonoses. It is true that they occur in tropical areas, but nothing prevents them from reaching Europe or the USA in the bodies of passengers of transcontinental airplanes. The export of tropical animals can also spread the virus to a distant region of the world.
These diseases raise legitimate fear because there is no effective medicine or vaccine. Symptoms of the disease can be nightmare – in extreme cases, we deal with a patient bleeding simultaneously from the nose, eyes, anus, mouth, lungs, in whom a light touch of the skin causes bleeding. If, after returning from the tropics, we feel even the slightest ailments, we should immediately see a doctor and tell us where we have been and how long we have returned to the country. Generally, viral hemorrhagic fever can be ruled out three weeks after the onset of disturbing symptoms, but even then one cannot calm down, because perhaps we were caught by, for example, malaria – not so spectacular, but equally dangerous.
The high mobility of humanity and interference in the most inaccessible places on Earth can lead to the opening of the microbial Pandora’s Box. It is possible that there are viruses somewhere more deadly than all known so far, waiting only for contact with humans. The known HIV virus, although not so deadly, but still torment, probably comes from monkeys. They have described a very similar virus, SIV, which is a “relative of HIV”. It is likely that the SIV mutation resulted in HIV attacking humans. Nature can be erratic, and we humans still know too little about it to be masters of the Earth.
Text: Tomasz Gosiewski, MD, PhD
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