It's hard to ignore the daily headlines about the coronavirus outbreak, with the disease now officially called COVID-19. The latest dour news reports the virus now has a foothold in South Korea, Iran, and Italy, and the most recent count is staggering. According to the World Health Organization, the disease has now spread to 29 countries, as the number of global cases has surpassed 79,000 (with the majority still in China), resulting in more than 2,600 casualties.  

The most recent updates have sent the stock market into a downward spiral, with the Dow Jones Industrial Average (^DJI -0.86%), the S&P 500 (^GSPC -0.60%), and the NASDAQ (^IXIC -1.08%) all down by more than 3% on Monday.

While the fear and uncertainty surrounding this global outbreak are certainly understandable, here are three things investors should remember in the wake of the outbreak and the resulting market decline.

Woman at a table grabbing her head in surprise while looking at her computer screen.

Image source: Getty Images.

1. Stick to your plan

In times like these, it can be unnerving to watch the market plummet, particularly in the face of glaring headlines that trumpet the massive point total or percentage loss of the major indexes, or "worst day in X years."

While it's easier said than done, ignore these panic-inducing headlines and stick to your guns. Most investors have a plan, whether it's investing a certain dollar amount each payday, having a specific percentage of your earnings allocated to your retirement fund, or adding to your emergency fund. Plans are made when cooler heads prevail and provide a template for what to do. Whatever your plan -- stick to it.

2. Back away from the sell button

The old idiom -- buy low, sell high -- is never achieved if an investor gives into fear and sells stocks in the midst of a general stock market meltdown, particularly one that could be short-lived. Investors widely profess to be in it for the long haul, until the unexpected happens, sending the market into a sharp decline.

Negative emotions -- like fear -- caused by external factors beyond our control are never an investor's friend, often leading to inappropriate investment decisions, like selling at the first sign of a market downturn.

It's important to remember that just as stocks go up, they also go down -- probably more often than you realize -- with the average correction occurring about every two years, and lesser downturns are even more frequent. That doesn't make them any less concerning while they're happening. It's best to keep your emotions in check and not make any rash decisions, especially since they will likely cause you to sell at precisely the wrong time.

3. This too shall pass

While it's tempting to think that the sky is falling, the reality is much different. In fact, this isn't the first time the world has faced a coronavirus. 

In 2003, there was a global outbreak of Severe Acute Respiratory Syndrome or SARS -- also within the family of coronaviruses -- which caused a public health emergency around the world. Over an eight-month period, there were more than 8,000 cases reported across the globe, infecting people in 29 different countries, eventually causing 774 fatalities. During the outbreak, thousands of people were quarantined, travel was restricted, many major cities looked like ghost towns, and borders were closed.

If that all sounds eerily familiar, it should. The important thing to remember is that within several months, the epidemic was contained. It's worth noting that in the years since, the world has dealt with bouts of Avian Flu, Swine Flu, MERS, Ebola, and Zika viruses.

As the old saying goes, "This, too, shall pass."