Dave: Norbert, does it seem like infectious disease outbreaks are more common today?

Norbert: It feels that way! I'm thinking of the highly publicized ones like Ebola, Zika, MERS and SARS viruses, but that leaves out common ones like measles or the yearly flu. Better detection and reporting partly explain why we're hearing more about these outbreaks, but it is also because it is happening more.

There are four reasons: modern transportation, urbanization, poverty, and climate change. While Jules Verne's "Around the World in 80 Days" was once fanciful, today, you can arrive anywhere in the world within 24 hours. In contrast, in the middle ages, it took traders years to bring plague from the Far East to Europe. But now, within one day, a man infected with Ebola brought the virus from Liberia to Dallas and infected two healthcare workers.

Another reason is urbanization. Today half the world's people live in crowded cities, making them vulnerable and increasing the spread of infectious diseases.

In some large cities, this is exacerbated by poverty where slums lack proper resources. The Ebola outbreak in West Africa killed more than eleven thousand people because they didn't have advanced medicines, facilities or a proper public health response.

The last factor is climate change. Higher temperatures can change the locations of disease vectors, such as mosquitos or ticks that spread disease and put new groups of people at risk.

Since we won't stop flying and I doubt we'll all move to the country, we should prepare for the spread of infectious diseases. We need proper responses to outbreaks, funding for research, and to develop medicines to protect us from the assault of these microbes.