How do they trace the origin of an outbreak of a viral disease?

One of the first things scientists and the general public ask after a big illness epidemic is, “Where did this originate from?” To predict and prevent future outbreaks, it’s necessary to understand where the viruses that cause pandemics like COVID-19 come from. This isn’t a simple job. It took 20 years to figure out where HIV came from and how it spread throughout the world. Even though Ebola has produced recurring outbreaks since the 1970s, scientists are still unsure of its genesis. To trace the origin of an outbreak of a viral disease necessitates a mix of lengthy fieldwork, comprehensive lab testing, and a good deal of luck. Perhaps the HIV pandemic might have been prevented if the circulation of HIV had been discovered in Africa shortly after the virus transitioned from wild primates to people.

The virus that transmits from animal to human

When a new zoonotic illness appears in a human population, it is critical to discover and identify the pathogenic agent as soon as possible. This early diagnosis is crucial for preventing outbreaks and epidemics. It’s tempting to begin the viral origin investigation by looking for sick animals around the first known human infection site, but wild hosts don’t always show symptoms. Viruses and their hosts adapt to one other over time, therefore illness symptoms typically don’t appear until the virus has migrated to a new host species. It’s not enough for researchers to look for ill animals. Another issue is that people and their food animals aren’t always in the same place. The location where researchers discover the first sick individual is not always the same as the location where the virus originally appeared. Bats were the obvious first place to look in the case of COVID-19. They’re recognised hosts for a variety of coronaviruses and are a possible source of zoonotic illnesses like SARS and MERS. Early detection, monitoring, and survey of the viruses circulating among humans are critical for preventing the re-emergence of a viral illness in a human community.

The monitoring to trace the origin of an outbreak of a viral disease should be done primarily in sentinel populations (I) living in areas near the habitats of animals considered to be important viral reservoirs (for example, rodents, bats, pigs, and monkeys); (II) living or working near animal breeding regions or slaughtering regions, as these locations provide ideal conditions for the emergence of human viral diseases related to human-nonhuman animal cohabitation; and (III) residing in viral vector-infested areas (especially mosquitoes). Nonetheless, this surveillance should be done on individuals who seek medical help with symptoms of viral infections. The absence of tools and techniques to undertake this control is, however, a real issue. A global need exists for the development of technologies that can quickly, accurately, and affordably identify a wide range of viral infections. Such instruments would largely be used in underdeveloped nations with tropical climates to improve healthcare services. Knowing which diseases circulate in a community will allow even minor alterations in circulation patterns to be detected.

Next step to trace the origin of an outbreak of a viral disease

The next stage is to see how closely a putative animal virus is linked to a human-infecting virus. Scientists do this by establishing the virus’s genetic sequence, which entails determining the order of the genome’s fundamental building components, or nucleotides. The more nucleotides that two genetic sequences have in common, the closer they are. Various techniques have been developed that compare the genetic sequences and correlate the similarities.

Knowing which diseases circulate in a community will allow even minor alterations in circulation patterns to be detected. A survey like this might help on several fronts, including the identification of viral illnesses where the causal agents are often unknown. Even though pathogen identification has no clinical or therapeutic implications in these situations, the data is important for epidemiological purposes.


Thus it can be concluded, viruses that can cause fresh epidemics are already “out there.” The monitoring of viral circulation in biological samples (human and non-human) is critical for the early detection of outbreaks or epidemics. In poor tropical nations, where individuals typically live in discord, the necessity for such surveillance and monitoring behaviour is much higher. If samples from (I) vectors, (II) resident viral reservoirs, (III) migratory animals such as birds, and (IV) people were used, the suggested surveillance would be even more successful.

Data collected from people and other animals (wild, cattle, and domesticated) would reveal where viral hotspots are located, allowing for steps to be taken to restrict viral disease transmission. Such a method might minimise not only health issues but also economic losses caused by illness and even death of economically valuable animals (for the food industry, for example).