Welcome to Burden of Proof, a regular column in which Julia Belluz (a journalist) and Steven Hoffman (an academic) join forces to tackle the most pressing health issues of our time - especially bugs, drugs, and pseudoscience thugs - and uncover the best science behind them. Have suggestions or comments? Email Belluz and Hoffman or Tweet us @juliaoftoronto and @shoffmania. You can see previous columns here.



Over the last several months, our collective attention has been poured into Ebola. As a journalist and academic, we've seen this in the newsroom and the lab. At Vox, we've had an Ebola lead to follow or story to tell nearly every day. The interest in Ebola reports has been high — among journalists and readers — and the anomalous and devastating nature of a global Ebola epidemic has meant that we've followed the story closely, even though this is a disease that will not have an immediate impact on our readership.



In the research lab, attention has been similarly diverted. Journals have put aside routine health topics to publish new Ebola research. This means that non-Ebola publications has been delayed or may never see the light of day and peer-review for papers that aren't related to this virus is taking longer than usual.



Of course, the Ebola exposure is mostly a good thing: this virus has been around for more than 30 years and rarely captured enough attention and resources to address its dangers or bring vaccines and treatments to market. But while our minds have been Ebola-focused, we've been ignoring other emerging health issues, some that hit very close to home. Here are four you need to know about:

1) There's a Chikungunya epidemic raging on

A viral disease called Chikungunya — that had never appeared in the Western hemisphere until last year — has been quietly sweeping the globe, reaching 37 countries and more than 335,000 people since December.



There's currently an outbreak in the Caribbean and Central and South America that continues to rage on with no sign of stopping. And the Centers for Disease Control and Prevention in the US is worried, warning American travelers last week to beware of painful mosquito bites.



Chikungunya means "that which bends up," referring to the contorted physique of an afflicted person That's because Chikungunya — pronounced chik-en-gun-ye — is transmitted to humans by mosquitoes. The virus brings on a high fever, headache, and severe joint pain that can persist for weeks or months. The name of this disease reflects those symptoms: it derives from a word in the Makonde language of Tanzania, where it was discovered in 1952, and it means "that which bends up," referring to the contorted physique of a person afflicted by the virus.



This year, more than 1,600 travelers returning to the US have been diagnosed with Chikungunya. For context, there are usually less than 30 Americans who get this virus each year.



So this is a disease epidemic with new and surprising characteristics — and we've mostly ignored it. There is no cure for Chikungunya and symptoms can be debilitating and potentially fatal, which has health officials concerned. They're also puzzled by Chikungunya's sudden appearance in the Western Hemisphere, and wondering whether it means this mosquito-borne disease will become a permanent feature here, spreading from bugs to people and back.

2) Enterovirus D68 may be paralyzing children



Since August, parents across the United States have been wondering about Enterovirus D68. First discovered in 1962, the virus has only rarely appeared in the US, so it was something of a mystery to doctors when, starting last summer, it began spreading among children, reaching 45 states by the end of October.



Though EV-D68 is believed to usually cause severe respiratory infections, this year the virus has been linked to the temporary paralysis of more than 50 kids as well as several deaths.



Enteroviruses circulate every summer and fall, usually making an appearance as a "summer cold." But why this more severe strain suddenly turned up with such force, leading to the largest-ever outbreak, remains a puzzle. And a virus that can paralyze children is a very frightening thing, recalling the pre-vaccine days of polio and iron lungs.



Is Enterovirus-D58 really causing kids to become paralyzed? How deadly is it? What are the things we don't know about this virus? How worried do parents need to be and which children are most at risk? Where will it go from here? These are questions this largest-ever outbreak will hopefully help researchers answer.

3) Measles is making a comeback

Measles is much less exotic than Ebola or Chikungunya but it's ringing alarm bells again because it's making a comeback in the US.



Though measles was declared eliminated here in 2000, according to a new New England Journal of Medicine article, there were more measles cases reported in America so far in 2014 than during any year in the past two decades.



The author thinks there are two key reasons for this resurgence:

First, though significant progress has been made in reducing global measles incidence, there is still substantial circulation of the virus in other countries. Susceptible U.S. residents who travel to countries where measles is endemic or epidemic and susceptible residents of those countries who travel to the United States are bringing the virus here.



Second, an increasing number of parents in this country are hesitant to have their children vaccinated, and such hesitancy has resulted in an accumulation of unvaccinated populations who can become infected and maintain transmission.



This is especially worrisome, considering how easily measles spreads (it's airborne) and that it can kill.



In a recent article in The Week, the author points out that readers should be more worried about measles than Ebola: it just takes an infected person breathing or coughing near someone who is unvaccinated. One case of Ebola, on average, leads to the infection of 1.5 to 2.2 other people. "By contrast, a person with measles is infectious for several days before they become sick. And a person with measles will on average infect 12 to 18 additional people."



Worldwide, 330 people die of measles every day. According to the World Health Organization, in 2012 there were 122,000 measles deaths globally which means measles remains among the leading causes of death among young children despite the availability of an effective vaccine. So any uptick in this disease anywhere is worth paying attention to.



4) Health systems in West Africa are falling apart

Some of the larger, systemic issues that have been worsened by Ebola have been shelved — but they may kill more people than Ebola ever will. With all eyes on crisis management, few people are thinking about what the virus has done to the routine work of local health systems. The short answer: devastation.

Ebola has stretched the already weak health systems of Guinea, Liberia and Sierra Leone to the very edge and beyond. Many of the few hospitals in these West African countries have closed because of Ebola. Doctors and nurses have died, or have walked off the job out of fear. This means that people with non-Ebola health needs — childhood vaccines, broken arms, maternity check-ins, HIV/AIDS testing or treatment — are not getting the care they would normally.



Though these effects are more difficult to count than Ebola cases and deaths, the outcome of such stress on the health system is going to be an avalanche of ill-health and untreated conditions.



So the real Ebola death toll in West Africa is much higher than reported for two reasons: there is widespread under-counting of cases, the World Health Organization has warned. But it's also that most Ebola victims are not dying from the virus itself but from everything else for which health systems can no longer offer care.

The one thing we often ignore that drives all health



Wealth disparities may not stir up our fear or capture our attention the way an exotic virus does, but they are probably the single most important influence on health everywhere.



Study after study has shown that being poor doesn't just affect health by lowering people's access to health care, but also by affecting the pre-conditions needed to live a healthy life, such as the ability to purchase healthy food, live in a clean environment, work in safe places, be free from violence, and demand fair treatment.



And it's not just the poorest of the poor we need to worry about. Perhaps the most surprising thing about poverty is that it affects health everywhere and produces what has been called a social gradient in health. This is how the World Health Organization explains it:

The poorest of the poor, around the world, have the worst health. Within countries, the evidence shows that in general the lower an individual’s socioeconomic position the worse their health. There is a social gradient in health that runs from top to bottom of the socioeconomic spectrum. This is a global phenomenon, seen in low, middle and high income countries. The social gradient in health means that health inequities affect everyone. For example, if you look at under-5 mortality rates by levels of household wealth you see that within counties the relation between socioeconomic level and health is graded. The poorest have the highest under-5 mortality rates, and people in the second highest quintile of household wealth have higher mortality in their offspring than those in the highest quintile. This is the social gradient in health.

This effect is present in poor and rich countries alike. Take the United Kingdom as an example, where we see that death rates for groups of people steadily increasing as you go from least deprived to most deprived:

The Ebola epidemic highlighted the fact that inequalities in health are driven by inequalities in wealth. As we saw this year, Ebola has been a treatable disease in America, but it’s deadly in Africa, where the survival rate has hovered around 30 percent. It's poverty that underlies this gap and many others that affect health.



While the Ebola outbreak has corralled global attention, we need to remember that the driving forces behind so much ill-health around the world are often less cinematic and frightening, perhaps even less newsworthy, but far more insidious.

