N 1347, an epidemic of unimaginable ferocity getting worse. Pathogens began circulating struck Europe. People first experienced flu- regularly among humans only after we started Ilike symptoms, but within days painful farming and settled in towns. One reason was swellings developed, which turned black, that we caught infections from our livestock: split open and oozed pus and blood. The Great flu from ducks, tuberculosis from cows. Pestilence, later dubbed the Black Death, swept But crucially, there were enough of us in close across the continent within four years, killing proximity that a germ could always find a new up to half the population. The disease host and keep spreading, persisting among persisted in Europe until the 1700s, always people and adapting to us. circulating somewhere, killing people off. Now we are crowding into cities and We speak of it nowadays as history. In fact, it travelling more, especially within the tropics is more like natural history: infectious disease where pathogen diversity is highest. That plus is part of the ecology of our species. Until globalised trade, migration and climate 1900, and despite considerable competition change reshuffle wildlife, people and from violence and starvation, it was our pathogens. Farms and towns invade the biggest killer, causing half of all human habitats of animals with viruses that can jump deaths. Now, it accounts for fewer than a to us, or to our densely packed livestock, also quarter of all deaths worldwide, most of them booming as demand for animal protein soars. in poor, tropical regions. In rich countries it is Public health experts have been warning only a few per cent. And the toll is falling. for years of “emerging” diseases, which can But we shouldn’t be complacent: plagues go from unknown to epidemic if the pathogen will return. The 1960s notion that infectious mutates or the ecology of its hosts changes to disease was on the way out ended when HIV make its spread easier. And it is viruses that appeared in the 1980s. Since then, many epidemiologists are most worried about. infections like bird flu, SARS and Zika have Bacteria can be deadly, and antibiotic caused alarm. But it took a near-disaster – resistance could mean diseases from the worst ever outbreak of Ebola – to scare gonorrhoea to ordinary bladder infections the inertia out of governments. As a result, become incurable, but work has at least begun we are at last preparing for the inevitable. on new drugs. In contrast, viruses can evolve A clutch of programmes being launched this and spread faster, there are thousands we year will improve our grip on microbial killers. know nothing about, and we have few drugs And the world now has an emergency medical against them. The worst emerging infections response team – which, astonishingly, it never since 2000 have all been viruses. had before. But we aren’t there yet. If a novel None is more alarming than the 2014 virus struck now, we would still be in trouble. outbreak of Ebola in West Africa. The virus For all our high-tech modernity, and in infected 50 times more people than any many ways, because of it, the risk that new previous outbreak, and reached big cities BRIAN LAROSSA BRIAN infectious diseases will evolve is actually for the first time. As a bat virus still > The coming plague A killer pandemic is now more likely than ever. Where will it come from and how can we beat it, asks Debora MacKenzie 25 February 2017 | NewScientist | 29 unaccustomed to humans, it spread fairly slowly, but an even slower international response allowed it to kill more than 11,000 people before old-fashioned methods, like isolating cases and quarantining their contacts, snuffed the outbreak out. There was no other option. We were unable to produce a vaccine in time even though we already had experimental Ebola drugs and vaccines, and their deployment was accelerated, with regulation and manufacture taking months instead of the usual years. Researchers have since discovered that as it spread the Ebola virus was adapting to people, and getting better at transmitting. It almost spiralled out of control in Nigeria. “The world was close to an abyss,” says Tom Frieden, outgoing head of the US Centers for Disease Control and Prevention. To combat the next plague, we will need vaccines, drugs and diagnostic tools – and just as importantly, some way to deploy them effectively. “We do not have that,” says Jeremy Farrar, head of UK medical research agency the Wellcome Trust. But we might if, in the wake of Ebola, we can build on momentum in three key areas: working out what the enemy is, arming ourselves against it and being ready to act forcefully and fast. KNOW YOUR and his colleagues at the pathogens. They have found dengue and West Nile. Last University of Edinburgh, UK, 984 viruses, 815 of them new November, he reported that the ENEMY reviewed what we know about to science. In the process, they more species a flavivirus regularly First, what should we such viruses. They identified have mapped hotspots of viral infects, the more likely it is to prepare for? “Spotting 37 already able to spread from diversity and trained and infect humans as well. That makes the next HIV or SARS human to human, though equipped local labs to test for the riskiest flaviviruses a clutch of before it strikes is poorly, that could become more viruses and watch for disease. virtual unknowns: Usutu – a bird- virtually impossible,” contagious. These range from borne virus invading Europe – says Ab Osterhaus, head virtual unknowns like o’nyong- Ilheus, louping ill, Wesselsbron of the new Research nyong, an African virus that Predicting risk and Tyuleniy. Center for Emerging Infections causes debilitating joint pain, But which of these viruses should The Global Virome Project 1and Zoonoses in Hannover, to Rift Valley fever, a common we focus on? Some are obvious, wants to go further in learning Germany. “There are too many livestock illness. such as a Chinese virus closely about the enemy, genetically viruses in too many species, That’s just the viruses we know. related to SARS but different sequencing and mapping most of interacting with humans and A project called PREDICT, funded enough that prototype SARS the estimated half-million so-far evolving in unpredictable ways.” by the US Agency for International vaccines won’t work against it. undiscovered viruses in families To narrow the field, he says, we Development, is looking for Others might be identified using we know can infect humans. It need “a detailed understanding of others. In places, mostly tropical, a clue discovered by Kevin Olival reckons it will need $3.4 billion to when, where and how viruses are where humans and wild of the EcoHealth Alliance, who do that over the next decade, and moving from wildlife to people”. mammals interact, the project works with PREDICT. this year it will start canvassing Because, like the historical screens people, their food and He has statistically analysed all for funds. The hope is that plagues, the next big disease is their rodent, bat and primate the available data on the flavivirus knowing what viral diversity likely to be one that has made the neighbours, looking for genetic family, a troublesome lot carried exists and where could provide leap from other animals to us. sequences of viruses in families by mosquitoes and ticks that unexpected insights and spur In December, Mark Woolhouse known to spawn human includes yellow fever, Zika, investment in disease control. 30 | NewScientist | 25 February 2017 ARM YOURSELF THE NINE VIRUSES OF THE APOCALYPSE Once we know what we are These are the diseases the World Crimean-Congo fighting, we have to arm Health Organization thinks we should haemorrhagic fever ourselves. Finding weapons find remedies for, fast. The first six Found across Africa, Asia and won’t be easy, though. The are its highest priority. south-east Europe, the virus is vaccines that defeated so many invading new territory as its tick infectious diseases in the 20th Lassa fever hosts capitalise on global warming. century were mostly made by This West African virus, It appeared in western Europe in government-owned firms that carried by the common 2010. Infected people generally have didn’t have to turn a profit and produced what Natal multimammate rat, a mild fever but some strains cause 2was needed as a “public good”. In the 1980s, infects 300,000 people severe haemorrhagic disease, with everything was privatised. That was good for a year. Most have no bleeding internally and from orifices, spurring profitable medicines for chronic symptoms, but it can cause from which 30 per cent of people die. conditions. But much medical innovation is diarrhoea and vomiting, then internal now done by small, start-up biotech firms, fluid accumulation, bleeding from Chikungunya which can’t afford to shepherd their products orifices, shock, seizure and coma. A virus spread by Aedes mosquitoes through the “valley of death” – the long, It kills some 5000 people annually. between monkeys and small expensive process of testing for safety and Initial symptoms resemble other local mammals in East Africa, Chikungunya efficacy, and establishing manufacturing diseases, making diagnosis tricky – started causing large epidemics processes and formulations for licensing. Only one reason West Africa was slow to around 2000 and exploded into Asia big pharma companies have the know-how spot Ebola. in 2005, after mutations made it and the $1 billion or so needed to bring a new better adapted to a new mosquito vaccine to market. But vaccines for common Nipah host. In 2014, it invaded the Americas diseases offer little profit; those against a virus This bat virus started and has occurred in Europe.