One of the biggest threats to public health right now is influenza. But it is only just emerging that scientists are beginning to wonder if we should be worried about a less familiar threat — and whether the disease is being understudied.

B. Respiratory syncytial virus, or B. Res, is a lung viral disease related to the virus that causes the common cold. B. Res infections cause milder symptoms, similar to the common cold, but they are worrisome because there are indications it can cause severe illness. One 2015 study compared the levels of B. Res infection with those of influenza across the world and found that it was much more common in poorer countries. In the last 10 years, infections have become more and more common in Asia and Africa, especially in some of the world’s largest cities. The World Health Organization says that high concentrations of people living in close quarters, such as crowded subways, buses and homes, could fuel B. Res epidemics.

With its low risk of spreading globally, the threat of B. Res is not likely to be in the near future, but while only a small number of infections occur, they can be life-threatening and claim the lives of children and the elderly.

Researchers with WHO have found evidence that B. Res outbreaks are more likely to occur in Asia because of the lack of a large recorded population of people and because these diseases are associated with higher economic development. WHO is trying to figure out if there are any advantages in terms of economic development or public health that can be gained by low-resource countries with high-risk diseases such as malaria or tuberculosis.

“We know it occurs in some Middle Eastern countries, including Lebanon, and we know it is a huge burden in Asia,” said Roberto van Velze, an infectious disease specialist with WHO. “This is one way where development is playing an important role.”

Similar challenges could result from an emerging epidemic of another disease, such as Middle East respiratory syndrome coronavirus, or MERS-CoV. Like B. Res, MERS-CoV is mostly limited to low-income countries. The same 2010 study that showed the extent of B. Res was one of the first studies to analyze the extent of MERS infection in the Middle East. But MERS currently is only in the Middle East and not a global threat. There has been limited research into what would be the implications of MERS-CoV spreading to more high-income countries and how well the infrastructure would be able to handle the strain. But if a major outbreak of MERS-CoV is to happen, poor countries would bear a disproportionate responsibility, even though they would be ill-equipped to handle the disease.