The world of Tzu Chi April 2020 (Vol.121)

2020 • 04 54 umanistic Medicine Translated by Lim Wen Xin e Perils of Cross-infection between Animals and Humans A re zoonotic diseases, or infectious diseases that are transmitted from animals to humans, solely caused by viruses? The short answer is no. Apart from viruses, these diseases are caused by other microorganisms such as bacteria, fungi and parasites, collectively known as pathogens. Humans are vulnerable to contracting an infection through direct contact with the excrement of disease-stricken animals or animal bites. In some cases, the transmission of diseases occurs via intermediate agents carrying the disease pathogen, such as mosquitoes, fleas and ticks, or through the consumption of food and water that have been contaminated by the excrement of diseased animals. As of now, there are many other modes of transmission associated with these zoonotic diseases that have yet to be verified. In Malaysia, dengue fever ranks high on the list of zoonotic diseases. A century ago, the dengue virus circulated among apes through the Aedes mosquito. Now, the virus has evolved to enable transmission between humans, albeit through the same medium. The rising temperatures caused by climate change and global warming and the congested living conditions as a result of urbanization create a conducive environment for mosquitoes to breed and accelerate the spread of the The total number of fatalities caused by influenza epidemics throughout human history has collectively exceeded that of World War II. We shudder at the atrocities of warfare, but tend to turn a blind eye to the fatal consequences of zoonotic diseases. mosquito-borne virus, particularly in erratic weather conditions. Humans are also vulnerable to another zoonotic disease – acquired immunodeficiency syndrome or AIDS. It is caused by the human immunodeficiency virus (HIV) that had been passed from apes to humans. HIV is transmitted between humans via exposure to contaminated blood through the sharing of syringe needles and blood transfusion, or semen through sexual intercourse, among others. According to 2018 statistics by the World Health Organization (WHO), about 32 million people had died of HIV globally since the beginning of the epidemic. Host-pathogen interaction Animals reared as livestock are among the major host organisms for H1N1, H5N1 and other high-risk influenza viruses stemming from zoonotic diseases. The H1N1 or swine flu virus is endemic in pigs and spread to humans from infected pigs, triggering a worldwide influenza outbreak that resulted in over 150,000 deaths globally. Meanwhile, chickens were identified as carriers of the H5N1 or avian influenza virus. The list goes on; the myriad strains of influenza virus are too numerous to mention. In an unprecedented record in history, the total number of fatalities