At the start of 2020, Moderna had a market capitalization of around $6.5 billion. Today, it's worth close to 10 times that amount. It has been a 10-bagger investment within just a few years, thanks to its COVID-19 vaccine.

One company that investors may be hoping to follow in its footsteps is SIGA Technologies (SIGA 3.50%). With a monkeypox treatment that could be vital in addressing the latest health emergency, SIGA's business could benefit from an influx of orders.

Monkeypox cases continue to rise

Earlier this month, the U.S. government declared the outbreak of monkeypox as a public health emergency. The first case in the U.S. emerged in May, and today, the Centers for Disease Control and Prevention (CDC) estimate that there are around 12,000 cases. Globally, case numbers top more than 36,000.

The positive is that the number of deaths is just 12. However, treatment may still be necessary for monkeypox, as the illness can last up to four weeks and cause many flu-like symptoms. 

This is where Siga's monkeypox treatment, Tpoxx, comes into play. It has been approved to treat monkeypox in Europe and the U.K. And in the U.S., while the Food and Drug Administration (FDA) hasn't approved it, Tpoxx is available under "compassionate use" through the CDC.

A game-changer for Siga?

Siga released its latest quarterly results on Aug. 4, with the business reporting sales of $16.7 million for the period ended June 30. That's 92% higher than the $8.7 million Siga reported in the prior-year period. The healthcare company credits the growth to rising oral Tpoxx sales to a new jurisdiction in Asia-Pacific and the U.S. Department of Defense.

Siga expects more growth ahead and notes that as of the end of July, it  has received international orders totaling $60 million this year, with nine of the 10 jurisdictions placing orders being new customers.

It's early on for Siga, and its sales will likely continue climbing as monkeypox continues to spread and countries look to stockpile treatments. However, it's a long shot at best for the business to generate the type of money that Moderna has brought in from its COVID-19 vaccine; Moderna projects its sales will top $21 billion this year.

The key uncertainty for investors is not knowing how long monkeypox will be around and how many competing treatments there might end up being. Currently, there is no treatment that the FDA has approved to treat monkeypox, and Tpoxx is the only one that it notes is available through the CDC.

Don't count on Siga being the next Moderna

It wouldn't be surprising for Siga's stock to rise along with concerns around monkeypox, not unlike how Moderna's shares increased as the rise in COVID-19 cases was a big concern for the public. However, the key difference I see is that as Moderna has made mRNA technology more popular thanks to its vaccine, it can use it for more than just COVID-19. The company is now using mRNA to develop other vaccines, including for the flu, respiratory syncytial virus, and cytomegalovirus.

In Siga's case, its pipeline centers around possible uses for Tpoxx, which are likely going to be far more limited. Prior to the monkeypox outbreak, Siga's top customers were the Canadian and U.S. governments, which were stockpiling Tpoxx -- also used to treat smallpox -- as a precaution against potential bioterrorism. 

Monkeypox may lead to an increase in sales of Tpoxx in the months ahead, but it's not a reason to invest in Siga for the long term. Although it may rise in value, there's little reason to suggest that it can be as successful as Moderna has been or be as good of an investment.