Fragile and vulnerable settings
Over 6.1 billion people live in unstable environments, where crises (such as war and mass population displacement) can leave them without adequate food, water, or basic medical care.
Ebola and other high-threat pathogens
The Democratic Republic of Congo saw several Ebola outbreaks last year, which spread to densely populated cities, making the epidemics even more difficult to tackle.
As well as Ebola, the WHO list SARS, Zika, Nipah, and the ominously-named "disease X" as pathogens that we need to prepare properly for. Before you panic and think you have symptoms, "disease X" is a codename for an as-yet-unknown disease that could arise and spread through the population.
The WHO have been quick to sound the alarm on antibiotic resistance, and this year it makes the list of biggest threats to humanity once again.
"A post-antibiotic era – in which common infections and minor injuries can kill – far from being an apocalyptic fantasy, is instead a very real possibility for the 21st Century," the WHO warned in 2014. Other than a few promising studies on new types of antibiotics, not much has changed and alarming scenarios for what happens when antibiotics stop working still loom large.
With 40 percent of the population at risk of dengue fever, it remains one of the biggest threats to world health. The mosquito-borne disease kills up to 20 percent of people with severe forms of the disease, mainly occurring during rainy seasons in countries like India and Bangladesh.
Progress tackling HIV has been enormous, but still nearly a million people a year die of HIV and/or AIDS. With more than 37 million people living with the infection, the WHO remains committed to tackling it head-on.
One of the biggest problems in doing so is reaching groups around the world often excluded from health systems, such as "sex workers, people in prison, men who have sex with men, or transgender people".
This year they warn that young women and girls are increasingly at risk of contracting HIV, citing that one in four HIV infections in sub-Saharan Africa occur in this group, despite the fact they only make up 10 percent of the population.
Weak primary health care
Many low-middle income countries around the world do not yet have adequate primary health care (the first point of contact people have with their health system) and it's putting lives at risk. In a global conference in 2018, all countries committed to improving primary health care. The WHO will work with countries and organizations to help improve this vital first port of call.