Unraveling the Causes Behind the Surge in Novel Viral Infections

If you have been following the news lately, you might have noticed that COVID-19 is not the only virus that is causing concern. In fact, there are several other viruses that have been emerging or re-emerging in different parts of the world, such as bird flu, mpox and Marburg. What are these viruses and why do they seem to be popping up more frequently? In this blog post, we will try to answer these questions and explain some of the factors that contribute to viral emergence.

What are bird flu, mpox and Marburg?

Bird flu is a term that refers to a group of influenza viruses that mainly infect birds, but can sometimes jump to humans or other animals. There are many types of bird flu viruses, but some of them are more dangerous than others. For example, H5N1 and H7N9 are highly pathogenic avian influenza (HPAI) viruses that can cause severe disease and death in humans. These viruses usually spread from direct contact with infected birds or their droppings, feathers or secretions. However, there is also a risk of human-to-human transmission if the virus mutates or reassorts with other influenza viruses.

Mpox (formerly known as monkeypox) is a rare viral disease that affects both humans and animals. It is caused by a virus that belongs to the same family as smallpox (Poxviridae), but it is less contagious and less deadly than smallpox. Mpox causes fever, headache, muscle pain and rash that can develop into fluid-filled blisters on the skin. The virus can spread from direct contact with infected animals (such as rodents or primates) or their bodily fluids, or from person-to-person contact through respiratory droplets or skin lesions.

Marburg virus disease (MVD) is a severe hemorrhagic fever caused by a virus that belongs to the same family as Ebola (Filoviridae). It can cause high fever, headache, vomiting, diarrhea and bleeding from various organs. The virus can spread from direct contact with infected animals (such as bats or monkeys) or their bodily fluids, or from person-to-person contact through blood or other body fluids.

Why do so many viruses seem to be emerging right now?

There is no simple answer to this question, as viral emergence is influenced by many factors that interact in complex ways. However, some of the main drivers of viral emergence include:

• Human activities: As humans expand their population and activities into new areas, they come into closer contact with wildlife and their habitats. This increases the chances of exposure to novel viruses that may have adapted to infect animals but not humans. For example,

  • Agriculture: Farming practices such as intensive animal husbandry create crowded conditions for livestock and poultry where diseases can easily spread among them or spill over to humans.
  • Deforestation: Cutting down forests for logging, mining, agriculture, urbanization, etc., reduces biodiversity, alters ecosystems, displaces wildlife, increases human-wildlife conflict, etc., creating opportunities for zoonotic transmission.
  • Bushmeat trade: Hunting wild animals for food, medicine, trophies, etc., exposes hunters, traders, consumers, etc., to potentially infected animals or their body parts.

• Climate change: As global temperatures rise due to greenhouse gas emissions, weather patterns change, affecting natural habitats, animal migration, vector distribution, etc., creating new conditions for viral survival, replication, transmission, evolution, etc.

  For example:

  • Arboviruses: These are viruses transmitted by arthropods such as mosquitoes, ticks, sandflies, etc., which depend on temperature, humidity, rainfall, vegetation cover, etc., for their development and activity. Climate change may expand their range into new areas where they encounter new hosts (human or animal) who may not have immunity against them.

  • Waterborne viruses: These are viruses transmitted through contaminated water sources such as rivers, lakes, wells, etc., which may be affected by changes in precipitation patterns such as droughts, floods, melting glaciers, sea level rise, etc.

• About 75 percent of new infectious diseases are caused by zoonosis. viruses can jump from one species to another, causing new diseases in humans or animals. This is called zoonosis. Some examples of zoonotic viruses are HIV, Ebola, SARS-CoV-2 (the virus that causes COVID) and influenza (the virus that causes flu). These viruses can originate from different sources such as bats, monkeys, pigs or birds.

• Other factors: Viruses are ancient organisms that have been around for billions of years. They are constantly mutating and exchanging genetic material with other viruses or cells. This allows them to infect different species and overcome their immune defences.

  However, not all mutations are beneficial for viruses. Some may reduce their ability to replicate or transmit. Others may make them more virulent or resistant to drugs or vaccines. The outcome of viral evolution depends on many factors, such as natural selection, genetic drift, recombination and reassortment.

  • Natural selection is the process by which viruses that have an advantage over others survive and reproduce more efficiently. For example, a virus that can evade antibodies or antiviral drugs will have a higher chance of spreading than one that can't.

  • Genetic drift is the random change in viral frequency due to chance events. For example, a virus that infects a small population may lose some of its diversity due to random sampling errors.

  • Recombination is the exchange of genetic material between different strains of the same virus during infection. For example, two strains of the influenza virus may swap segments of their genomes and create a new hybrid strain.

  • Reassortment is similar to recombination but occurs between different types of viruses that share the same host cell. For example, an avian influenza virus and a human influenza virus may mix their genes and produce a novel strain that can infect both birds and humans.

These processes can lead to the emergence of new or re-emerging viruses that pose a threat to public health. However, viral evolution alone is not enough to cause an outbreak. There are also other factors that influence how viruses jump from animals to humans or spread among people.

One of these factors is human behaviour and activity. As humans expand their population and territory, they come into contact with more animals and their habitats. This increases the risk of zoonotic transmission - when a virus jumps from an animal reservoir to a human host.

• Zoonotic transmission can occur through direct contact with infected animals or their bodily fluids; indirect contact with contaminated objects or surfaces; ingestion of infected food or water; inhalation of aerosols; or bites from vectors like mosquitoes or ticks.

  • Some examples of zoonotic viruses include monkeypox (which originated from rodents), bird flu (which originated from poultry), Marburg (which originated from bats), Ebola (which originated from bats), SARS-CoV-2 (which originated from bats), HIV (which originated from primates) and rabies (which originated from dogs).

Another factor that affects viral emergence is urbanization and globalization. As humans move into densely populated areas with poor sanitation and healthcare systems, they create favourable conditions for viral transmission and amplification.

Urbanization also facilitates human mobility and travel across regions and continents. This allows viruses to spread quickly among different populations with varying levels of immunity and susceptibility.

• Some examples of urbanized viruses include dengue (which spreads through mosquitoes in tropical cities), measles (which spreads through respiratory droplets in crowded places), yellow fever (which spreads through mosquitoes in urban slums) and COVID-19 (which spreads through respiratory droplets in various settings).