Modern Australian
Men's Weekly

.

Humans are to blame for the rise in dangerous viral infections

  • Written by Justine R. Smith, Professor of Eye & Vision Health, Flinders University

Today, we hear about dangerous viral infections around the world on a regular basis. Social media and internet access may be an obvious explanation for their seeming increase.

But it doesn’t just seem this way. The number of viruses and the infections they cause are truly increasing. Scientific advances, the way humans live today and virus biology all contribute to the rise of viruses.

Read more: Health Check: when are we most likely to catch viral diseases?

New viruses, all the time

It seems viral infections are everywhere these days. Starting from January 2018, Nigeria has been experiencing an unusually large outbreak of haemorrhagic fever caused by Lassa virus. There have been more than 400 confirmed infections and 100 deaths to date.

The southern Indian state of Kerala is battling an outbreak of the rare Nipah virus, which causes severe inflammation of the brain and claimed the lives of 14 people in May.

The Brazilian outbreak of viral yellow fever that began in late 2017 has moved into highly populated areas near São Paulo and Rio de Janeiro. One-third of the 723 people with confirmed infections have so far died from the illness.

Humans are to blame for the rise in dangerous viral infections Brazil is currently in the midst of a yellow fever outbreak. Fernando Bizerra Jr./EPA

We’re no doubt more aware of such serious diseases after the unprecedented 2014-2016 Ebola outbreak in West Africa that claimed more than 11,000 lives. And then the 2015-2017 Zika virus outbreak that closely followed during which 3,500 babies were born with nervous system or eye damage.

Read more: Zika, dengue, yellow fever: what are flaviviruses?

The first report of human virus infection was yellow fever in the US army at the turn of the 20th century. And now, estimates suggest three to four new species of human viruses are found each year and around 250 human virus species are yet to be discovered.

Discovery of a new virus today is complex and requires many steps. Typically, it involves describing its complete genetic code with a combination of intensive molecular sequencing work in the laboratory and computational analyses using enormous reference databases.

Medical epidemiological studies (that look at the distribution of disease) and biological experiments are then needed to understand any virus as a dangerous human pathogen. It may then take some time to link a virus with a particular human disease.

Humans are to blame for the rise in dangerous viral infections Human parechoviruses were only discovered in the 1950s. from shutterstock.com

For instance, human parechoviruses (which can cause severe disease in young children) were discovered in the 1950s. But they were only identified as a cause of disease in young children in 2004. And relatively large Australian epidemics since 2013 have highlighted their link to a serious sepsis-like illness and potential for developmental complications.

How humans contribute

Modern humans contribute to the success of dangerous viruses. A virus replicates only when inside the cell of a living being, and spreads most efficiently when there is contact between two individuals.

The United Nations measures current world population growth at more than 1% per year. From the virus’ perspective, potential incubators are increasing. The world’s population is also urbanising, which means people living in closer proximity, which is conducive to spread of a virus.

Domestic and international mass transport permit viruses to move between regional populations.

Many dangerous virus infections are zoonoses, which are diseases transmitted to humans from other animals. Bats are a common culprit – one theory is that a unique low-grade immune system allows them to carry a relatively high number of viruses without developing disease. Epidemics caused by severe acute respiratory syndrome (SARS) coronavirus probably began through bat-human contact.

Read more: Why bats don't get get sick from the deadly diseases they carry

Expanding settlement towards wilderness areas provides more opportunities for viruses to meet people. Domesticated livestock may carry viruses that infect humans, and the growing human population dictates increasing and more compact livestock production.

Influenza virus infects pigs, cattle and poultry as well as humans. The H7N9 strain that has infected more than 1,500 people in China and resulted in the death of one-third since 2013, first moved to humans from diseased poultry.

Humans are to blame for the rise in dangerous viral infections The H7N9 virus first moved to humans from diseased poultry. Si Chuan/EPA/AAP

When it comes to numbers though, the most important viral transporter is the mosquito. The bite of certain Aedes mosquitoes, for instance, is the primary route for infection with dengue, Zika and chikungunya viruses. Queensland is home to these mosquitoes, so outbreaks of dengue occur annually, usually due to an infected traveller arriving from an endemic region.

Research conducted in the Amazon has linked expansion of the mosquito range in endemic areas to deforestation and low re-vegetation. Resistance to the relatively few available insecticides may also contribute to their population growth.

Why viruses are sneaky

The basic biology of viruses contributes to their capacity to cause disease. Most human viruses replicate almost instantaneously and in huge numbers. As a result, mutations arise at a high rate in the genetic code of a virus. This allows the virus to adapt quickly to an adverse environment, such as the human immune system or drugs. It may also allow a virus to jump from an animal host to humans.

Read more: New mosquito threats shift risks from our swamps to our suburbs

Some viruses establish a chronic infection, which extends the potential for transmission. After acute illness, Ebola virus hides for many months in parts of the body that generate weak inflammatory responses, such as the sexual organs, the brain and/or the eye.

And although human immunodeficiency virus (HIV) may cause an acute illness, there is usually a long delay between infection and the onset of any disease. Consequently infected people may pass on HIV for years before being aware that they carry the virus.

Humans are to blame for the rise in dangerous viral infections Mosquitoes are responsible for the most viral transmissions. from shutterstock.com

There are no specific drugs for most dangerous human viruses. This is in part because viruses are a fast growing and diverse group, with no common drug targets to exploit, as has been possible with antibiotics for bacteria.

But another challenge relates to the viral life cycle, which uses the infected person’s cell machinery. Drugs that target the growth of viruses therefore have effects on the person’s cell, which may result in drug side effects.

Read more: HIV latency: a high-stakes game of hide and seek

Also, the capacity of a virus to adapt implies the potential to develop resistance to a drug. Drug treatment for HIV infection involves a combination of drugs with different actions to address this problem.

Despite the many challenges associated with dangerous viruses, research continues to yield even more innovative solutions. The World Mosquito Program, run out of Monash University, is one example. This program is based on the discovery that a safe and natural bacteria, Wolbachia, stops viral growth in the mosquito. Insects in regions endemic with mosquito-borne diseases are being infected with Wolbachia to break the transmission cycle.

Ultimately, the cunning strategies used by dangerous viruses are no match for the wide breadth of human ingenuity.

Authors: Justine R. Smith, Professor of Eye & Vision Health, Flinders University

Read more http://theconversation.com/humans-are-to-blame-for-the-rise-in-dangerous-viral-infections-94747

Powering Shepparton’s Businesses: Expert Commercial Electrical Services You Can Count On

When it comes to running a successful business, having reliable, compliant, and efficient electrical systems is non-negotiable. From small retail ou...

Maximise Efficiency: Cleaner Solar Panels for Optimal Performance

Solar panels are a smart investment in energy efficiency, sustainability, and long-term savings—especially here in Cairns, where the tropical sun ...

7 Common Air Conditioner Issues in Melbourne – And How to Fix Them

Image by freepik Living in Melbourne, we all know how unpredictable the weather can be. One moment it’s cold and windy, the next it’s a scorchin...

Powering Palm QLD with Reliable Electrical Solutions

Image by pvproductions on Freepik When it comes to finding a trustworthy electrician Palm QLD locals can count on, the team at East Coast Sparkies s...

The Smart Way to Grow Online: SEO Management Sydney Businesses Can Rely On

If you’re a Sydney-based business owner, you already know the digital space is crowded. But with the right strategy, you don’t need to shout the...

What Your Car Says About You: The Personality Behind the Vehicle

You can tell a lot about someone by the car they drive—or at least, that’s what people think. True Blue Mobile Mechanics reckon the car says a l...

The Confidence Curve: Why Boudoir Photography Is the Empowerment Trend You Didn’t Know You Needed

Boudoir photography has been quietly taking over social feeds, Pinterest boards, and personal milestones—and for good reason. It’s not just abou...

Understanding Level 2 Electricians: Why Sydney Residents Need Licenced Experts for Complex Electrical Work

When it comes to electrical work around the home or business, not all electricians are created equal. In Sydney, particularly when you're dealing wi...

Retirement Anchored in Model Boat Building for Waterford’s Doug Unsold

WATERFORD — When Doug Unsold sees his ship come in, it’s usually one he’s crafted with his own hands. The 67-year-old retiree from Waterford ...

The Science Behind Alarm Clocks and Your Circadian Rhythm

Waking up on time isn’t just about setting an alarm—it’s about working with your body, not against it. At the heart of every restful night and...

How to Use Plants to Create a Calming Atmosphere in Your Home

In today’s fast-paced world, cultivating a calm, soothing environment at home has never been more important. Whether you live in a busy urban apar...

How Maths Tutoring Can Help Students Master Maths

Mathematics can be a daunting subject for many students, often causing stress and frustration. However, maths tutoring has proven to be an effective...

Refurbished iPads Are Better Than New Ones (Here's Why)

Image by rawpixel.com on Freepik Apple's refurbished iPad program has quietly become one of the best deals in tech. While everyone obsesses over the ...

Your Guide to Finding the Right GP: What Perth City Doctors Offer Today

Choosing a General Practitioner (GP) is one of the most important health decisions you’ll make. Luckily, Perth’s vibrant CBD now hosts a new ge...

Why Every Mining Operation Needs a Robust Safety Management System

Mining is one of the backbones of the Australian economy, particularly in Western Australia. Back in 2019-20, mining contributed 10.4% of Australiaâ...

Australian Classic Literature Enjoys Resurgence

Welcome back to the good old days of storytelling! As the modern world becomes increasingly more demanding, returning to childhood favourites offers...

How to Choose the Right Lawyers in Sydney for Your Situation

When faced with a legal issue, selecting the right legal representation can make all the difference. Whether you're dealing with a personal injury, ...

Building a Governance Model for Headless Content Management at Scale

Image by pch.vector on Freepik There's never been a better time to implement a headless content management system (CMS) to gain the flexibility and ...