World at mercy of emerging new infections

Viruses are quick studies. They are prolific at adapting to new environments and infecting new hosts.

As a result, they are able to jump the species divide from animals to humans — as the new coronavirus in China is showing. It is estimated that 89 percent of one particular family of viruses, known as RNA

viruses, are zoonotic in origin.

This means that they started in animals and have since become established among humans. RNA viruses are notorious for being able to mutate in a range of environments.

This family of viruses includes everything from Ebola and West Nile Fever to measles and the common cold.

The Severe Acute Respiratory Syndrome-related coronavirus (or SARS-CoV)

that broke out in Asia in 2003 is also an

RNA virus; so too is the significantly more virulent and fatal Middle East respiratory syndrome coronavirus ( MERS? CoV), first identified in Saudi Arabia in 2012.

Both are zoonotic. SARS-CoV is believed — although it is never been confirmed — to have originated in bats. Infected dromedary camels are thought to have been the source for MERS-CoV. Overall around 10 percent of those infected with SARS died.

The mortality rate for MERS is estimated to be around 35 percent. Seven human coronaviruses ( HCoVs) have been identified to date: two in the 1960s, and five since SARS in 2003. It is the seventh that is now making headlines.

Latest virus on the block

In December 2019, a number of people fell ill with what was soon confirmed to be a newly identified coronavirus, provisionally dubbed 2019-nCoV.

At this stage, it is suspected but not confirmed that the outbreak originated in one seafood market in Wuhan, a city some 1 126 kilometres south of Beijing. The market has been closed since January 1. The virus has, thanks to modern international travel, reportedly spread to five other countries: Thailand, Japan, South

Korea, Taiwan and the US.

On the African continent, authorities in Ivory Coast were on January 27 testing a suspected case of the virus in a student who returned to the country from China over the weekend.

As with other coronaviruses, 2019-nCoV is zoonotic in origin. While it is too early to confirm, it appears that 2019-CoV is what is known as a recombinant virus.

This means it bears the genetic material of both bats and snakes, suggesting that the virus jumped from bats to snakes in the wild — and then, of course, to humans.

Coronaviruses were originally associated with a wide spectrum of respiratory, intestinal, liver and neurological diseases in animals. In the 1960s, with the advancement of laboratory techniques, the first two HCoVs ( HCoV- 229E and HCoV-OC43)

were isolated from patients.

These were associated with upper respiratory tract infections, causing mild coldlike symptoms. For this reason, the circulation of HCoVs in the human population was not monitored and no vaccines or drugs were developed to treat CoV infections.

Then, since the outbreak of severe acute respiratory syndrome in China in 2003, five additional human coronaviruses were identified — SARS-CoV (2003), HCoV-NL63

(2004), HCoV-HKU1 (2004), MERS-CoV (2012),

and now 2019-nCoV.

As with SARS, the elderly, especially those with existing health conditions, are the most vulnerable to 2019-nCoV. The outbreak is not entirely unexpected. Coronaviruses are among the emerging pathogens that the World Health Organisation ( WHO) in 2015 identified as likely to cause severe outbreaks in the near future.

For a long time is was difficult to identify the causative agent of infectious diseases. The rapid development of various molecular detection tools has enabled researchers to identify several new respiratory viruses.

It has also helped with the characterisation of novel emergent strains.

This was what scientists were able to do within weeks of the first case of the Wuhan coronavirus.

An emerging infection

Coronavirus infections also fall within the crop of diseases known as emerging infectious diseases or newly emerging infectious diseases. These are infections that: have recently appeared within a population, or whose incidence or geographic range is rapidly increasing, or at the very least threaten to increase in the near future.

As with SARS and MERS, many emerging diseases arise when infectious agents in animals known as zoonoses are passed to humans. As the human population expands and populates new geographical regions — often at the expense of wildlife — the possibility that humans will come into close contact with animal species that are potential hosts of an infectious agent increases. Combined with increases in human density and mobility, it is easy to see that this combination poses a serious threat to human health. Each of these diseases has come with societal and economic repercussions. Apart from illnesses and deaths, travel, business and daily life are affected. There is also always the risk of public fear and economic losses.

High risk

There is an ever-increasing diversity of animal coronavirus species, especially in bats. So the likelihood of viral genetic recombination leading to future outbreaks is high. The threat of future pandemics is real as highly pathogenic coronaviruses continue to spill over from animal sources into the human population.

Misdiagnosis of future outbreaks poses an additional threat to healthcare workers, with hospital-based spread to other patients putting further pressure on already strained healthcare systems.

Burtram Fielding is director (research development and principal investigator) of the Molecular Biology and Virology Research Laboratory Department of Medical BioSciences at the University of the Western Cape.