Why viruses are not just a threat but also a driver of better health - Thoughts from the Centre | Deloitte UK

By Márcia Costa and Emily May, managers in the Deloitte Centre for Health Solutions


Viruses tend to have a bad reputation. The recent COVID-19 pandemic did not do them any favours and every winter, when flu and norovirus cases soar, we have an unavoidable reminder of the risk viruses pose and just how dangerous they can be. The word virus itself is derived from the Latin word poison. However, viruses are not always against us. In fact, we graciously host a wide variety of them, primarily in our gut, forming part of the body’s microbiome which is crucial in safeguarding our health. Other viruses can help in diagnosing and treating cancer and bacterial infections and improve our understanding of other diseases. In this blog, we explore the nature of viruses and their use in our lives to shine a positive light on these often underappreciated benefits viruses bring.1

Lshc-jan25-inline1Viruses – unalive parasites!

Viruses are small infectious agents that rely on the living cells of animals, plants or bacteria to multiply. They are parasites as they depend on host cells for most life-sustaining functions. They are composed of a genetic core, which can be either DNA- or RNA-based, enveloped by a protective protein-based covering. Some viruses are also further protected by fat and protein molecules. The amount and arrangement of the proteins and nucleic acid of viruses vary considerably and determines their size and shape (ranging from 20-30 nanometres (nm) to around 250-400 nm). Due to their lack of cells, they have been excluded from the plant, animal and prokaryotic bacteria groups, meaning they have been given their own kingdom.2

There has been substantial debate about whether they are an organism - a living thing - but there’s a broad consensus that that they are not largely because they are unable to reproduce, maintain homeostasis or perform metabolic processes (i.e., produce energy) independently.3 Instead, they highjack the living aspects of the cells to manage these processes. This concept of viruses effectively being parasites adds to the list of reasons to dislike them. Their parasitic nature means that viruses use these host cells to replicate (i.e., create exact copies of themselves,). This causes direct and indirect damage to cells, which can lead to disease.4

Viruses and bacteria are often confused. Figure 1 explains the key differences between these two common types of pathogen.

Figure 1: Key differences between viruses and bacteria


Source: Deloitte analysis, 2024

So why do our bodies happily host them?

Viruses are abundant and exist almost everywhere on Earth: an estimated 10 nonillion (1031) individual viruses exist on our planet, in fact there are more viruses on Earth than stars in the Universe.5 Many are discovered every year, but of those 1031 viruses, just 200 have been identified which are known to infect, sicken or kill us.6 Our rapidly expanding knowledge of human biology makes it clear that we are not primarily made up of ‘human’ cells that are occasionally invaded by microbes; our bodies are really superorganisms of cohabitating cells, bacteria, fungi and, most numerous of all, viruses – as much as half of all the biological matter in your body is not human.7

The human body hosts a community of 380 trillion viruses - the human virome – which has a far-reaching positive influence on our health.8 Most of our viral colonies live in the gut, but the quantity and prevalence in other locations varies widely between individuals. Although much is unknown about the human virome, many of these viruses known as bacteriophages (eaters of bacteria) simply coexist with us as part of our microbiome, a few can cause illness, but many protect us from infections and trigger the development of innate immunity, and keep pathogenic bacteria in check.9 Nevertheless, changes in their diversity and concentration have also been associated with several conditions, including type 2 diabetes, Chron’s disease, and several types of cancer.10

We routinely speak about the good and bad bacteria in our bodies, the food and drink we consume and all aspects of our lives. Viruses fall into those same categories, but, like bacteria, the challenge is to figure out how to limit the bad ones and promote the good.

Beneficial use cases of viruses

One of the most successful public health use cases is in prophylactic or preventative vaccines, which involves a weaker or dead form of a virus being introduced into the body stimulating the body to create antibodies and build up immunity and importantly, a memory of the virus. When the virus comes in full force, the body already knows how to fight it. This was the science behind the world’s first vaccine in which cowpox, a virus that caused mild symptoms in humans, was used to fight and subsequently eradicate the deadly smallpox virus.11

As our understanding of biology and genetics has evolved, we have also been able to ‘engineer’ viruses in our favour, including to help us treat many conditions. These include:

  • Gene therapy – this type of therapy is used for the treatment of a genetic disease, such as cancer, cystic fibrosis, heart disease, diabetes, haemophilia and AIDS, by the introduction of specific cell function-altering genetic material into a patient (to correct what has gone wrong genetically-wise). Since viruses are good at infecting cells, they have been used as the vehicles to transport this genetic material.12
  • Oncolytic viruses to treat cancer – acting as an immunotherapy, these viruses infect only the tumour cells. The virus replicates multiple times within the cell to the point that the cell membrane bursts, killing their host cells and therefore triggering an immune response against cancerous cells.13
  • Bacteriophages - because viruses can infect bacteria, they can also be used as bacteriophage therapy which is particularly useful as the concern with multidrug-resistant bacteria grows. The main advantage is that, unlike antibiotics, these phages can be ‘engineered’ to target only the intended bacterial cells without affecting the ‘good’ gut microbiome.14
  • Infection to fend off more dangerous viruses and bacteria - an asymptomatic blood-borne virus known as ‘GB virus C’, slows the progression to AIDS in people with HIV and lowers the death risk of Ebola virus. Even harmful viruses can harbour disease-combating strategies such as the hepatitis A virus providing protection against hepatitis C, and researchers have used lymphoma-associated viruses to cure type 1 diabetes in mice.15
  • A de facto immune system - viruses have been found bound to the surface of mucosal membranes, such as those found in the nose, throat, stomach and intestines. They cannot replicate there so lie in wait for a vulnerable host. If a food contaminated with salmonella bacteria is consumed, for example, the surface bound virus could infect the bacteria and kill them before they can cause disease.16
  • Next generation vaccines – A harmless virus is used to deliver the genetic code of the antigen you want the immune system to fight and triggers the body’s immune defence. For example, the Astra Zeneca and Johnson & Johnson COVID-19 vaccines used a viral vector, and many others are trialling the use of viral vectors are currently for a wide variety of diseases from HIV to bird flu.


Viruses tend to be seen solely as the bad guys, but there is a growing body of research evidence to show that they are also pretty vital to our health. As science and technology evolves, and we better understand how they work, we can certainly learn how to best use them to our advantage and equally to protect ourselves when things do not go well!


Márcia Costa - Research Manager, Life Sciences Insight Lead

Márcia is the research manager for healthcare in the Centre for Health Solutions, providing support and expertise to develop solutions to overcome today’s healthcare challenges. Working with the team, Márcia develops insights based on rigorous data analysis to improve outcomes for patients and increase health systems efficiencies. Originally from Portugal, Márcia has an MSc in biomedical engineering and biophysics and a PhD in cancer research. Márcia has previously worked in publishing for an oncology journal in London. Márcia is passionate about health equity.

Email | LinkedIn

LSHC blog 13 Jan author 1

Emily May, Assistant Manager, UK Centre for Health Solutions

Emily is an assistant manager in the Centre for Health Solutions where she applies her background in both scientific research and pharmaceutical analytics to produce supported insights for the Life Sciences and Healthcare practice. Emily leads the research and publication of the life sciences insights, performing thorough analysis to find solutions for the challenges impacting the industry and generating predictions for the future. Prior to joining the centre, Emily worked as an Analytical Scientist conducting physical chemistry analysis on early stage drug compounds and previously lived in Antwerp, Belgium where she researched and developed water-based adhesive films.

Email | LinkedIn



[1] The Microbiome and Viruses: What roles do they play?

[2] Virus | Definition, Structure, & Facts | Britannica

[3] Are viruses alive? And why does it matter? | Science News

[4] Viral Pathogenesis - Medical Microbiology - NCBI Bookshelf (nih.gov)

[5] There are more viruses than stars in the universe. Why do only some infect us? (nationalgeographic.com)

[6] Virus infection: How does the coronavirus infect cells? | Caltech Science Exchange

[7] https://www.scientificamerican.com/article/viruses-can-help-us-as-well-as-harm-us/

[8] https://pubmed.ncbi.nlm.nih.gov/36929732/

[9] The Microbiome and Viruses: What roles do they play? — Fidalgo Island Health Center

[10] The human virome: assembly, composition and host interactions | Nature Reviews Microbiology

[11] Frontiers | Edward Jenner and the Small Pox Vaccine (frontiersin.org)

[12] Viral vector platforms within the gene therapy landscape | Signal Transduction and Targeted Therapy (nature.com)

[13] Oncolytic virus therapy in cancer: A current review - PMC (nih.gov)

[14] Using Viruses to Kill Bacteria | MIT Technology Review

[15] https://magazine.hms.harvard.edu/articles/good-viruses-do

[16] https://www.scientificamerican.com/article/viruses-can-help-us-as-well-as-harm-us/


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