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Something strange is happening in the recent decades: new deadly viral infections, never seen before, are emerging and threatened millions of people. HIV, SARS, MERS and avian flu are the examples of such infections that got significant publicity and attention. What unites all these infections together is the fact that all of them originate from the wildlife. Viruses previously unknown to affect people are suddenly found in human populations and even, like HIV, spread worldwide.
MERS (Middle Eastern Respiratory Syndrome) is an interesting recent example. The virus causing this illness was first identified only in September 2012. By August 2013, around 100 patients, mostly in Saudi Arabia, were diagnosed with MERS, and half of them died as a result of this infection. The virus was declared by WHO as a “threat to entire world”. The source of the virus was traced to Egyptian tomb bat: most affected patients lived in or close to the buildings where these bats were found.
Bats are often associated with newly emerging viral infections
MERS is not an isolated example when viral infection gets transferred from bats to humans. Research has identified several horseshoe bat species from the genus Rhinolophus as the reservoir hosts for coronavirus that is associated with severe acute respiratory syndrome (SARS). The SARS outbreak in Southeast Asia in 2002 -2003 affected more than 8000 and killed 774 people. It was reported to be transmitted by Chinese Horseshoe bats. These bats are seen in China, India, Nepal, and Vietnam.
Ebola virus and Marburg virus, the infectious agents behind the viral hemorrhagic fever, got notoriety due to their deadly nature. These viruses belong to the Filoviridaefamily. Cases of Ebola virus infection have been reported in Democratic Republic of the Congo, Gabon, Sudan, Ivory Coast and Uganda. Closely related Marburg virus was first found in 1960s in Europe in German cities of Marburg and Frankfurt, as well as Yugoslavian capital Belgrade. Unusual location of this outbreak provided ground for a number of conspiracy theories about genetically manipulated and artificially produced deadly viruses.
There is no specific treatment for viral hemorrhagic fever caused by either of these two viruses. Supportive therapy in the form of intravenous fluids, oxygen inhalation, blood transfusion and organ system support is usually given in the hope that natural immune system will struggle the infection off. The patients are also kept in isolation since disease is highly contagious.
There are several other, less common, viral infections that can also be transferred by bats and, on some rare occasions, infect humans. Australian bat lyssavirus (ABLV) is related to rabies virus and may be transmitted by bite of a bat. It results in rabies like disease in human population and is usually fatal. The incubation period is 4 to 5 weeks. It is a very rare disease and few cases were reported in Australia. All infected persons have died. Rabies vaccine and immunoglobulin against rabies is protective against this virus.
Hendravirus, Nipah virus and Cedar Virus belong to the family of viruses called Paramyxoviridae. Hendra virus was first identified in 1994 in Australia after the death of one human and ten horses. These viruses are transmitted by Pteropid fruit bats or flying foxes. This infection is transmitted to human hosts by close contact with body fluids of infected horses. The horses get this infection from the fruit bats by eating food recently contaminated by flying fox urine or saliva and develop lung edema, congestion and neurological features. These viruses are not transmitted directly to humans.