On the morning of March 11, 1918, soldiers at Fort Riley, Kansas, suffered from high fevers, muscle aches and sore throats. Within days, thousands of American soldiers reported similar symptoms. Dirty and disorderly army camps around the country had exposed soldiers to diseases. Because of the influenza virus, 20 to 50 million people around the world lay dead a year later.

When American troops travelled across the Atlantic to support the Allies, influenza travelled with them. The virus sided with neither the Allies nor the Axis powers during World War I. After ravaging throughout Europe, influenza made its way into Asia and Africa by the summer of 1918. Despite the November armistice, influenza continued to cause international chaos. At the time, no effective drugs or vaccines were available, so American citizens wore masks, and public facilities closed down.

Throughout the next century, various other diseases have posed a threat to humankind. Most recently, the World Health Organization (WHO) declared the Zika virus an international public health emergency. The Zika virus is a mosquito-transmitted infection related to dengue, yellow fever and West Nile virus. After being discovered in Ugandaís Zika forest in 1947, the virus remained in Africa and Asia. It was not until last May that the virus was reported in Brazil. Within the last few weeks, cases of the virus have been reported in Illinois.
Few people are immune to the disease, allowing it to spread rapidly. In tropical regions of the Americas, millions of people have been affected. Some symptoms of the virus include aches, fatigue, fevers, conjunctivitis and rashes. For pregnant women, the Zika virus can have a serious birth defect on the brain of their child. Currently, there is no vaccine for the Zika virus, but efforts to create one have begun.