© Youssouf Bah/Associated Press
Health workers teach people about the Ebola virus and how to prevent infection in Conakry, Guinea, in March.
A Canadian man returning from Liberia recently alarmed health officials with fears that he might have the Ebola virus. Although in good health when he traveled, the man was admitted to the intensive-care unit in Saskatchewan with classic symptoms of the disease.

That health scare, and others in recent weeks, were a wake-up call to those who saw the outbreaks as an "African problem." They remind us that people - and their infections - are not bound by borders. To those who claim we can't afford foreign aid, I respond that we can't afford to think of health threats as "foreign" and "domestic."

Ebola is a deadly viral infection that many people first learned about through novels like "The Hot Zone" and the film "Contagion," which featured the specter of a deadly uncontrollable outbreak wreaking global havoc.

As a physician from Nigeria now researching infectious diseases at the University of Michigan, I'm not surprised by the Canadian scare - which turned out to be a false alarm. If anything, I'm surprised it didn't happen sooner.

Ebola is spread when people come in direct contact with blood or secretions from an infected person, or when they are exposed to contaminated objects, such as needles. This means patients should be treated in isolation. Ebola victims suffer skin rash, fever and internal bleeding. The World Health Organization reports that Ebola outbreaks have a fatality rate of up to 90%.

Today, we live in a connected world ripe for an Ebola pandemic. The infected may appear healthy for up to three weeks while transmitting it to unsuspecting people. In this age of high-speed travel, that person could tour the world three times over - all while unknowingly spreading the disease.

We've seen it before. In 2002, the deadly flu-like illness known as SARS broke out in China. Within a year, it killed nearly 800 people, including at least eight in the United States. The U.S. fared even worse during the H1N1 swine flu pandemic of 2009. Of the nearly half a million deaths, nearly 12,500 were American.

The death toll in the west African Ebola outbreak has risen to 142, and experts say it's a uniquely challenging outbreak.

We still do not have effective drugs or a vaccine to fight Ebola. There is simply not much incentive for pharmaceutical companies to invest in medical solutions when there is little chance of a financial return.

Where there is little private sector input, foreign aid can help. Unfortunately, many in the global north believe that foreign aid is not a good investment. A recent Kaiser Family Foundation survey showed that 61% of Americans thought that too much is being spent on foreign aid (incidentally, most people significantly over-estimate how much aid is given).

But there is nothing "foreign" about foreign aid. When it comes to infectious diseases, aid can be about self-protection, not altruism.

Take small pox. Once a global threat, smallpox was eradicated by "foreign aid," which supported the development of the first universally successful vaccine. With the same resolve, we can put an end to malaria, tuberculosis, HIV and even Ebola.

By investing in research for early diagnosis, treatment and vaccines for "African" diseases such as Ebola, we can make the type of progress that we have made with heart disease, diabetes and cancer. After all, we are more connected than we realize.