key: cord-0041903-483q0nia
authors: Greener, Mark
title: Emerging UK infections: identifying new threats early
date: 2019-03-25
journal: nan
DOI: 10.1002/psb.1746
sha: e76f52d167baaba77929f0dde9c5c75fbd1a84a1
doc_id: 41903
cord_uid: 483q0nia

Predicting which new and emerging pathogens will pose a threat to the UK population can be difficult. This article discusses the steps Public Health England and other government agencies are taking to identify new threats and protect the public against emerging infections.

T he microbiology results must have come as a shock. After all, you wouldn't expect monkeypox -an orthopox virus related to smallpox 1 -to turn up in a British seaside resort. Monkeypox usually infects people living in remote forested areas in West and Central Africa 1 and the infection had never been reported in Europe.

But within a week in September 2018, two unrelated cases of monkeypox in individuals from Nigeria presented in Cornwall and Blackpool. 2 And while monkeypox does not generally spread readily between people, 1 a healthcare professional caring for one of the patients before the infection was diagnosed contracted the virus. "This was the first person-to-person transmission recorded outside Africa," Professor Dilys Morgan MBE, Head of Emerging Infections at Public Health England (PHE), told Prescriber.

While PHE doesn't expect these cases to herald a monkeypox epidemic in the UK, it's not an isolated example of an unusual pathogen reaching these shores. Ebola (which kills, on average, half of those infected), severe acute respiratory syndrome ( Figure 1 . The Asian tiger mosquito (Aedes albopictus), a vector for many infectious diseases, is an emerging threat to the UK prescriber.co.uk threat -as shown by the recent cases of monkeypox in England." So, how can we expect the microbiologically unexpected?

Professor Morgan believes that emerging pathogens that pose the greatest threats to the UK include respiratory viruses, vector-borne diseases and gastrointestinal infections. "Any of these could be a new infection or the spread of a known, or slightly changed, organism," she says. New potentially fatal respiratory infections, for instance, include SARS and the Middle East respiratory syndrome (MERS) coronavirus. "The UK is at risk from new respiratory viruses or known viruses that have mutated or recombined to have a greater impact on human health, such as avian or human influenzas," Professor Morgan remarks.

Indeed, a century ago, Spanish influenza swept the world, even reaching Alaska and remote Pacific islands. 3, 4 Spanish flu may have infected up to half the world's population. 3 One in 20 of those infected died and, while it's difficult to be accurate, the pandemic probably killed between 50 million and 100 million people. 3, 5 Epidemics, pandemics and localised outbreaks emerge when the population has limited immunity to the new pathogen. Measles, for instance, killed one in five young children on Rotuma, an isolated Polynesian island, in 1911. The islanders had not previously encountered measles. 6 Bites of insects and other arthropods -such as mosquitoes, ticks and blackflies -can transmit several potentially serious infections, of which malaria is the most notorious. But there are numerous other threats. For instance, Ixodes ricinus -the deer or sheep tick -can transmit the bacterium Borrelia burgdorferi, which causes Lyme disease, the UK's most common tick-borne human infection, 7 with, PHE estimates, 2000 to 3000 new cases in England and Wales each year. 8 Pathogens carried by ticks also cause tick-borne encephalitis (TBE) -a viral infection that affects about 10,000 people across Europe each year -and rickettsioses, caused by members of the Rickettsia genus of bacteria. Species of Rickettsia can cause Rocky Mountain spotted fever, Mediterranean spotted fever and African tick-bite fever. In the UK, TBE and rickettsioses occur in returning travellers. However, British ticks now host pathogenic rickettsiae. 7 "At present, these infections pose minimal risk to the non-travelling public," Professor Morgan notes. "However, if the vectors become more common in the UK and the number of cases of infection among travellers from endemic areas increases, there is the potential for UK-acquired cases to occur."

Meanwhile, mosquito-borne diseases pose a constant threat. "The spread of the Asian tiger mosquito [Aedes albo pictus, see Figure 1 ] across Europe is a threat to the UK, because this is the vector for previously exotic infections such as chikungunya and dengue," Professor Morgan says. "We have already had two findings of the Asian tiger mosquito in South East England and in both cases, control was rapidly implemented." The mosquito Culex modestus, currently found around the Thames Estuary (see Figure 2) , could act as a vector for West Nile virus, although no human or animal cases have, as yet, been diagnosed that were transmitted by this insect in the UK.

In the future, climate change predictions suggest, Plasmodium vivax and, to lesser extent, P. falciparum -the protozoal parasites responsible for malariacould colonise parts of England. 9 There haven't been any confirmed cases of malaria from an endemic vector since the last indigenous case in England in the 1950s. 9,10 Nevertheless, during 2017, 1792 cases of imported malaria were reported in the UK. Despite being a notifiable disease, the current system seems to capture only around 56% of cases in England. 11 So, the true figure is probably closer to 3000 cases. In the future, climate change may allow sustained transmission of malaria in the UK. 9 So, it might only be a matter of time before endemic malaria makes a comeback.

Several factors account for the spread of many vector-borne diseases. Climate change, of course, contributes to the spread of some vectors from their traditional ranges. Human travel and trade routes are also influential. That's nothing new: analysis of personal hygiene sticks in a latrine at a relay station on the Silk Road at Xuanquanzhi in northern China dating from 111 BC to 109 AD revealed eggs of the Chinese liver fluke (Clonorchis sinensis), which is not endemic to the area. 12 More recently, A. albopictus might have reached the Netherlands in water pooled in used tyres. 9 "Novel methods of food production and the capacity to rapidly transport our food across the world means that potentially large numbers of people could quickly become affected by food-related pathogens," Professor Morgan says. "The outbreak of a novel Shiga toxinproducing Escherichia coli in Germany 

So, it seems likely that travellers and trade will continue to import exotic infections, while ecological changes will encourage some organisms to expand their ranges. But growing awareness of the threat posed by emerging infections may also have driven the increase in the number of reports. "The emergence of infections having a significant human impact has been fairly constant over the decades," Professor Morgan says. "However, there is better recognition of new and emerging infections or unusual syndromes because the world is now so well connected with rapid formal health systems and informal reporting. New molecular laboratory methods also facilitate the detection of 'new' pathogens."

Many emerging pathogens present with relatively non-specific symptoms. Initially, for example, monkeypox causes fever, chills, lymphadenopathy, headache, myalgia, backache and exhaustion. 1 Nevertheless, community healthcare professionals should watch for 'red flags' that might suggest an emerging infection. "Taking a travel and animal-contact history is essential when healthcare professionals are faced with assessing a patient with unusual symptoms, signs or syndromes," Professor Morgan suggests. "If in doubt, healthcare professionals should consult with their local infectious disease team." PHE and the government have implemented several lines of defence against emerging infections. As well as overseeing the system to detect and assess the risk from emerging infections, the Imported Fever Service (IFS) is a specialist advisory and diagnostic service for healthcare professionals who might be faced with a patient with fever and other symptoms on their return to the UK. PHE also runs the nationwide mosquito surveillance project in collaboration with a range of organisations, which monitors mosquitoes at seaports, airports, service stations on motorways and other key sites across Great Britain.

"We also have robust epidemic intelligence systems for detecting and assessing the risk for the UK population from infectious diseases either at home or abroad," Professor Morgan adds. For example, the multi-agency and crossdisciplinary Human Animal Infections and Risk Surveillance group (HAIRS) has met every month since February 2004 to identify and discuss emerging and zoonotic (a disease that can be transmitted from animals to humans) infections that may pose a threat to UK public health.

Indeed, most emerging infections are zoonotic. In 1957, for example, avian H2N2 and human H1N1 simultaneously infected a single animal. Reassortment produced a new H2N2 strain that caused the Asian flu pandemic, which killed about four million people. 13 Despite its name, monkeypox's natural hosts remain unknown. However, native African rodents including rope squirrels (Funisciurus species) and the Gambian pouched rat (Cricetomys gambianus) are the prime suspects. 2 Camels are a potential source of human infections with MERS. 14 The AIDS pandemic probably followed zoonotic transmission of HIV types 1 and 2 from African primates on multiple occasions. 15 "Exotic infections are always going to make the headlines, as shown by the recent monkeypox coverage, but we only have to look at the Ebola outbreak in West Africa in 2014/15 to realise that an outbreak anywhere in the world can have a major impact on the UK even though we have very few cases," Professor Morgan notes. "The Department of Health and Social Care and PHE will continue to be vigilant for the next emerging infection so that we can take whatever steps are needed to protect the public."

Monkeypox: infor mation for primary care

The invisible enemy

Modeling the impact of pandemic influenza on

Age-specific mortality during the 1918 influenza pandemic: Unravelling the mystery of high young adult mortality

The immune system: a very short introduction

Tick bite prevention and tick removal

Lyme disease: resources and guidance

Effect of climate change on vector-borne disease risk in the UK

From Shakespeare to Defoe: Malaria in England in the Little Ice

data • Public Health England. Human Animal Infections and Risk Surveillance group (HAIRS). www.gov.uk/government/collections/human-animal-infections-and-risksurveillance-group-hairs • Public Health England. Imported Fever Service. www.gov.uk/guidance/importedfever-service-ifs • Public Health England. Malaria: guidance, data and analysis. www.gov.uk/ government/collections/malaria-guidance-data-and-analysis • Public Health England. Mosquito: nationwide surveillance

Box 1. Further information on emerging infections in the UK prescriber

Malaria imported into the United Kingdom

Early evidence for travel with infectious diseases along the Silk Road: intestinal parasites from 2000 year-old personal hygiene sticks in a latrine at Xuanquanzhi Relay Station in China

Avian influenza virus (H5N1): A threat to human health

Middle East respiratory syndrome coronavirus specific antibodies in naturally exposed Israeli llamas, alpacas and camels

Origins of HIV and the AIDS pandemic

West Nile virus: epidemiology, diagnosis and prevention

Mark Greener is a full-time medical writer and journalist and, as such, regularly provides editorial and consultancy services to numerous pharmaceutical, biotechnology and device companies and their agencies, none of whom had any involvement in this feature. He has no shares or financial interests relevant to this article.Mark Greener is a freelance medical writer