Healthy outlook on life: Are infectious diseases as big a threat as we think?

Bill Gates says infectious disease is the biggest threat to humanity. From the HSE to binding international laws, the fight is ongoing — but are things really as dire as the billionaire makes out? Rita de Brún reports

The prospect of a highly contagious and deadly new disease spreading speedily around the globe is not something any of us like to dwell upon. Well-thumbed history books are filled with accounts of the Spanish flu that killed 50m in 1918.

Fast forward a hundred years and philanthropist and businessman Bill Gate is writing in a Business Insider op-ed: “Whether it occurs by quirk of nature or at the hand of a terrorist, epidemiologists say a fast-moving airborne pathogen could kill more than 30m people in less than a year.”

On an equally dour note, he later cautions that the world needs to prepare for same, in the way it prepares for war.

Gates is no fool, let’s face it, so it’s comforting to know public health emergency preparedness was at the very core of a conference on best practices in the implementation of the International Health Regulations (IHR), which recently took place.

The IHR are binding on 196 countries, including Ireland, and all World Health Organisation member states.

At the conference, dozens of expert EU/EEA and accession country professionals spoke on public health crisis preparedness, and on the co-ordination of responses to serious cross-border threats that may be caused by chemical, biological, radiological, or nuclear environmental agents and threats of an unknown origin.

Given protection was the core focus, it was apt the conference took place at the foot of the Acropolis; that most ancient of citadels, built high on a hill, chosen for purposes of defence.

Aleksandar Simunovic, an epidemiologist from the Croatian Institute of Public Health, spoke about the systematic monitoring, suppression, and prevention of contagious diseases that are integral parts of epidemiological surveillance, making the point that as infectious diseases and pathogens don’t respect borders, it’s vital that countries share epidemiological data, not only within Europe but globally.

“Intense international traffic causes agents of the various infectious diseases to travel easier and faster than ever before,” he says. “This ‘compression’ of space and time, along with global climate change, is a fertile ground for the emergence of many of the emergent and re-emergent contagious diseases that we’re witnessing today.”

The Department for Strengthened Disease Control, which he heads up, collects data on contagious diseases of public interest, to implement better analytics and prevent the spread of epidemics and the possibility of resistance to antibiotics. TB and Legionnaires’ disease are the most important contagious diseases under ‘special surveillance’ there.

The urgency of doing away with the stigmatisation of migrants, asylum seekers, and refugees, and the false assumption of their being a health threat, was one of the conference topics addressed. The point was made that massive screenings and mandatory examinations, unjustified from an epidemiological standpoint are not the solution.

It was well argued that the health response to these groups should be through the strengthening of national health systems rather than through “ad hoc dedicated parallel or second class services”. Also, that a “human rights and a right to health approach” must be adopted for these population groups.

Greece’s experience with displaced populations is well known. According to European Commission statistics, almost 857, 000 refugees and migrants arrived there in 2015, with close to 200,000 more arriving over the next two years. Today, in a year in which the country expects 32m travel visitors, an estimated 57,000 refugees and migrants are stranded there.

Theofilos Rosenberg, associate professor of surgery at the University of Athens and president of the board of the Hellenic Centre for Diseases Control and Prevention, played a core role in bringing the conference to Greece.

Theofilos Rosenberg, who says ‘we have to rise to challenges’ facing health systems

Alluding to that country’s recent economic difficulties and the continuing humanitarian crisis, he told the Irish Examiner: “A modern Greek tragedy has been performed for several years now, with unavoidable impacts on public health, the public health system, and Greek society.”

Asserting that the role of the Greek Public Health Agency “has never been more difficult”, he says: “We have to rise to these challenges and accomplish our mission to protect all residents of the Greek territory effectively, even with limited means.

“At the same time, we have to try our best to contribute efficiently to the concerted efforts of the international community to be prepared for and tackle health threats of international concern. In this respect, the implementation of the IHR is not just a legal obligation for our country but a prerequisite for the health security of all citizens, residents, and visitors in Greece.”

In Ireland, the HSE Health Protection Surveillance Centre (HSE-HPSC) is heavily involved in the implementation of the IHR. Public health emergency preparedness is core to its brief. Its infection surveillance systems provide a strong framework for pandemic response.

The World Health Organisation, European Centre for Disease Prevention and Control, and other parts of Ireland’s health, Defence Forces, and agriculture services, along with travel sector and port experts, are just some of those with whom it links in to implement the IHR.

As for the most significant infectious threat of our time, Dr Kevin Kelleher, director of the HSE Health Protection Surveillance Centre, says it’s antibiotic resistance.

Dr Kevin Kelleher, who says antibiotic resistance is the biggest threat.

There’s no denying that truth. Incidences of the superbug carbapenemase producing enterobacteriaceae (CPE) are increasing here year on year. CPE is the most difficult superbug to kill with antibiotics. In 2016, we had 280 such cases, double that of the previous year.

Despite the entirely excellent and diligent worldwide work being done across the globe in implementing the IHR, more needs to be done to protect against a global infectious disease pandemic.

More safe and effective vaccines must be created and distributed. More needs to be done to protect and maintain the health of all, particularly the poor, the displaced, and the weak. Global health is in peril when sickness festers and spreads, not just the unfortunates enduring the plight.

Dr Cillian De Gascun is a consultant virologist and director of the National Virus Reference Laboratory at UCD. Asked whether he shares Bill Gates’ stated belief that infectious disease is the biggest threat to humanity, he shakes his head: “It is not in the virus’ interest to eradicate its host, as then the virus dies.

“A virus will certainly kill people but what a virus ultimately wants to do is to co-exist with its host, not kill it.” So, infectious disease won’t wipe out humanity? “The potential for high mortality viruses with high attack rates is there. But it hasn’t happened yet for a reason, and that reason is probably that viruses as dangerous as the influenza H5N1 don’t seem to be able to become very transmissible. Or at least they haven’t managed to in the past 30 years.”

On the prospect of a novel deadly and highly contagious virus emerging from the abyss, Dr De Gascun muses: “Certainly it could. The avian influenza H7N9 virus has a mortality rate of about 40%. But it hasn’t become very readily transmissible and it hasn’t spread around the world the way the novel virus H1N1 did in just a matter of weeks in 2009.” So these viruses aren’t as clever as we fear? “It’s more that there are so many factors we don’t yet understand,” he replies.

What’s the biggest concern from a hypothetical perspective? “It’s that a virus like H5N1, which has a high mortality rate, but isn’t very transmissible, will recombine with our seasonal influenza virus which is very transmissible but not as severe, to form something of a hybrid in between the two.”

The biological makeup of the influenza genome makes that dire scenario a real possibility: “Because influenza has a segmented genome, recombination occurs quite readily and frequently.

“So that’s the concern,” he repeats, “that something with a very high mortality rate will combine with something that’s very transmissible.”

What is Ireland’s virus risk level?

Rita de Brún asks Dr Cillian De Gascun, consultant virologist and laboratory director at the UCD National Virus Reference Laboratory, which infectious diseases should most concern us

With Zika, SARS, MERS and Ebola having entered not just the zeitgeist but the world at large, Rita de Brún asks Dr Cillian De Gascun, consultant virologist and laboratory director at the UCD National Virus Reference Laboratory, which infectious diseases should most concern us.

WE don’t have any natural rubella circulating in Ireland, but there’s still a risk of imported cases.

Unfortunately, we’ve been a little less successful with measles in the last couple of years, in that our immunisation rates are not quite what they need to be. So, we’ve had imported cases that led to national outbreaks.

While we’re aspiring to eliminate and eradicate these pathogens (bacterium, virus, or another micro-organism that can cause disease), measles and rubella have seen a resurgence across Europe in recent years, largely caused by poor vaccine-uptake rates.


Irish vaccine uptake rates are typically 80 – 85%. For eradication purposes, we need to get those figures up, to over 90–95%. As for mandatory vaccination, I don’t know if we’re there, yet. It’s certainly something we should keep in our armoury.


Generally speaking, if humans are the reservoir for (as in the carriers of) the pathogens, as we are for measles and rubella, then we can achieve eradication with a vaccine programme.


Back in 2014 between 30 and 40 people were tested following an outbreak in West Africa. All tested negative.

Eradication is not achievable with ebola, because the reservoir for that is in nature, not in humans. Since we can’t eradicate it, we need to be able to control and monitor it.

While the ebola risk to the Irish general population is low, what can happen is that the infected person returns from holiday with a fever, and unless they’ve been in or near an ongoing outbreak of ebola, they’re unlikely to think a haemorrhagic fever (such as ebola) is the possible cause of their feeling unwell.

As for ebola and other haemorrhagic fevers, the reason they’re slightly more concerning is because, although we don’t have the natural reservoirs for them in Ireland — which may be the seasonal fruit bat, with non-human primates being the intermediate hosts — those who get infected overseas and return to Ireland may haemorrhage and, when they do, blood-spill could cause human-to-human spread.


We would have had somewhere in the region of 15-20 notifications during the Zika outbreak in South America and the Caribbean in 2015 and 2016.

Zika is transmitted by mosquitos. In Ireland, while we don’t have the species of mosquito you need to transmit the Zika virus, sexual transmission is a risk.

The natural reservoir for the Zika virus is probably a non-human primate, first discovered in Uganda in 1937, or thereabouts. Zika can’t be spread by coughing, sneezing, or respiratory droplets, in the way the common cold or influenza is.

So, because we don’t have the natural Zika reservoir, and we don’t have the mosquito that’s capable of transmitting it, in Ireland we would only have a very limited, person-to-person spread. In that way, the Zika risk here is quite low.


Malaria, too, is transmitted by mosquito. So, if a person returns — and it happens not infrequently — from visiting countries in which malaria is endemic, the primary risk is to the person that contracted malaria. There’s no real risk to co-workers or other family contacts, purely because the pathogen is typically transmitted through mosquito bite.


One virus that is more concerning is MERS coronavirus (Middle East respiratory syndrome coronavirus, or MERSCoV). Fortunately, that doesn’t spread from person-to-person very readily, but it can spread by respiratory droplet, in the same way as influenza or the common cold. You don’t need a mosquito to contract MERS-CoV.


As for the H7 and H9 influenza viruses that have been circulating in China for the past five years, while they have a very high mortality rate, they don’t seem to be as readily transmissible as our own, seasonal influenza.


Respiratory pathogens are probably the most concerning type, as the symptoms are like colds and flu and you might have it before you realise what’s going on. This scenario is in direct contrast to the case of a person returning from Sub-Saharan Africa and bleeding because of haemorrhagic disease. Should that happen, the correct diagnosis will be made fairly quickly. In that way, respiratory pathogens probably pose the greatest risk.

The approximate mortality rates are: SARS, 10%; seasonal flu, between 0.1% and 0.5%; MERS, 35 to 40% and H5N1 avian flu, 50%.

While these are high mortality rates, it’s the respiratory pathogens that are more concerning for us.

Somebody who has contracted one of those overseas may, thinking he has a cold or flu, spend hours travelling home on a plane, shedding virus all that time, unknowingly infecting other passengers, and others on arrival home.

So, while that’s the greater risk, the risk is still pretty small in Ireland. Protective and preventive global surveillance and data-sharing measures, overseen by the WHO, ECDC and others, ensure that, as a general rule, we’re informed before there’s a risk of an infectious disease coming to our shores.

Given Ireland’s current climate, the emergence of a new pathogen is unlikely, but not impossible that a brand-new pathogen is going to emerge here first. Many of the novel viruses we see — the influenza viruses — seem to come from the South East Asia region. Wet markets play a role in that. Ireland is naturally protected, because we don’t have a lot of the natural host reservoirs for these pathogens, and we don’t have the mosquitos that would transmit them.

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