Travel - not without consequence.

In 2017, the International Air Transport Association (IATA) reported that worldwide annual air passenger numbers exceeded four billion for the first time. In 2000, individuals on average flew once every 43 months. By 2017, this figure halved to once every 22 months. Cumulatively, the data reflect a global population on the move.

As our guest editors Dipti Patel and Hilary Simons point out, global travel has repercussions. Concerns around biosecurity hazards of travel are well reported, with a wide range of threats such as tuberculosis, typhoid and influenza. New threats have emerged in recent years such as severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) coronaviruses, multidrug-resistant gonococcus and carbapenem-resistant Enterobacteriaceae. In 2018, the United Kingdom had imported cases of monkey pox and Europe saw large outbreaks of measles, stoking fears of travel-associated transmission during the summer months. Advancements of transport technology has meant that the modern traveller can now travel much greater distances, across different time zones and continents, and to previously remote locations. Addressing the scale and rapidity of global travel presents a significant challenge that requires the development of new biosecurity measures that are cost-effective and timely.

People travel for different reasons, and in this themed issue, we present a selection of articles that illustrate the changing traveller profiles. Pavli et al. report how travellers from Greece were increasingly not holiday-goers but business travellers, who often travel for longer durations and frequencies abroad. Many are increasingly travelling to developing countries, but it appears with insufficient travel health precautions. Similarly, in the article by Bhuvan et al., the profile of trekkers visiting Nepal has changed. Previously, visitors from high-income countries in the West predominated, but increasingly more trekkers come from other parts of the world including China, with differing health needs and behaviours with regards to precautions taken.

Travellers today can access health information from diverse sources, both formal and informal. Squiers et al. describe how Zika risks and prevention measures were often communicated by the news media. This highlights a possible avenue for pushing out public health messaging for safe travel. However, as we have previously reported, there is also a potential risk of misleading or inaccurate health information being disseminated by mass media that are beyond the control of public health agencies.

Also of note, travel health risks in destination countries are dynamic. In their article, Peterson et al. report how better sanitation levels and lower hepatitis A prevalence in several countries mean hepatitis A vaccination may no longer be required for travellers. Consequently, having up-to-date and accurate health intelligence on destination countries is essential for health services to prepare for and deal with the health consequences associated with travel.

As a final thought, the ability (and desire) to travel is increasingly an expectation of those who can afford it. However, there are also environmental and climatic consequences that we may uncomfortably choose to ignore. Global travel has a carbon footprint that contributes to global warming and climate change. Most modes of transport generate some form of pollution that has direct health consequences: air pollution from vehicular emissions affects lung health and causes vascular diseases. Stopping travel entirely is unrealistic, but there remains a vital public health need and challenge to alter public behaviour and to advocate for less travel and less polluting modes of travel. Small changes in travel behaviour at the individual level cumulatively may bring considerable public health and planetary health benefits. As was reflected on the agenda at the recent World Economic Forum in Davos, sustainability and the need to tackle climate change remain key global health issues. Our actions are not without consequence.

In this issue

In addition to the themed articles on travel health, we have another excellent offering of articles from our authors this month. A common thread across many of them is about health consequences. The massive rise of non-communicable diseases globally in recent years poses significant health system challenges well into the future. The root causes are multifactorial, and unless they are addressed, as Al-alawy discusses in his article, they threaten the longer term sustainability of health systems. Poor diets and the lack of physical activity are well recognised as key drivers of the global obesity epidemic, and several of our articles explore this theme. Is skipping breakfast bad for children? Liu et al. think so. Their study found a possible correlation with missing breakfast and increases in non–high-density-lipoprotein cholesterol, a known risk factor for coronary heart disease in later life. Another article discusses how the availability of playground areas and their amenities is linked to deprivation and population density. Having good play spaces for children undoubtedly provides safe spaces for children to be physically active.

The issue of safety is iterated in another study in which the use of parks by adolescents was observed to be determined by their perception of road safety. Childhood trauma, and in particular traumatic brain injuries, can have pervasive health consequences. The study by Algnham et al. also found that injuries were associated not just with poorer general health but also with mental health in children. Interestingly, the mothers of children injured were also more likely to report suboptimal mental health. In another article, Meredith et al. report how although fatality rates associated with horse riding have been falling, injuries remain prevalent, highlighting a need perhaps for more work into protective measures.

Next, we have several articles that focus on health services. You et al. report on the determinants of breast and cervical screening in rural women in China. Unsurprisingly, socio-economic factors were found to be key determinants. However, what was also striking was how the lack of female health practitioners in primary care has a negative impact on screening uptake. Complementing this is an article by Laar et al. who demonstrate that mobile health technology can be a useful adjunct for maternal and child health services in rural Ghana which can help address equity issues in access. The article by Cheung et al. describes how despite being aware of their hepatitis B carrier status, women with chronic hepatitis B infection may still not be appropriately managed in pregnancy where there is a lack of continuity of care.

From a health protection angle, we have another article studying the health consequences of unconventional natural gas development (‘fracking’). This is a contentious and emotive issue in many countries, and evidence of the long-term consequences of this activity is slowly emerging. The article of the month is an important systematic review carried out by Torres et al. to identify the factors that determine self-medication with antibiotics in low- and middle-income countries. Worryingly, they found a high prevalence of self-medication, often for a range of minor ailments for which antibiotics are not indicated. This review highlights the monumental challenge we face in reducing the overuse of antibiotics, a vital action necessary to maintain the efficacy of antibiotics and to minimise the emergence of antibiotic resistance. A postantibiotic era where they are no longer effective against common infections is indeed a frightening prospect.