Mergers and acquisitions -- M&A -- are a key part of the health-care sector, with companies routinely buying other companies, as well as entering into joint ventures and collaborating on the development of specific drugs.

Indeed, 2014 has already seen notable M&A activity, with the purchase of a stake in Alnylam Pharmaceuticals (ALNY -0.95%) by Sanofi (SNY 0.68%) being yet another major deal in the health-care space.

The acquisition sees Sanofi purchase a 12% stake in Alnylam for $700 million, as the French-based company seeks to overcome the loss of patents on some of its best-selling drugs, with its research and development function seemingly unable to fill the void on its own. It also comes just a month after U.S. regulators rejected Sanofi’s potential blockbuster drug for multiple sclerosis, Lemtrada, which had been a key driver of the $20 billion 2011 takeover of Genzyme and, as such, was a major disappointment for the company.

Furthermore, as part of the deal, Sanofi and Alnylam will ramp up their research collaborations, with the focus being on treatments for rare genetic diseases, as management at Sanofi seeks to beef up the company’s drug pipeline. This arguably highlights that time is of the essence for current management, which is now entering its sixth year at Sanofi, and which needs to start delivering an improved top and bottom line so as to appease shareholders.

Sanofi’s purchase of a stake in Alnylam is not the only piece of M&A activity of recent weeks, with Shire (NASDAQ: SHPG) also announcing the successful completion of the tender offer for all of the outstanding shares of ViroPharma (NASDAQ: VPHM) for a total consideration of around $4.2 billion.

The deal could be significant for Shire, as it seeks to increase its focus on serious diseases, with ViroPharma’s development of drugs such as Cinryze (which is used to prevent and treat attacks of a genetic disorder called hereditary angioedema -- a swelling of the larynx) and maribavir (a potential treatment for a virus that can prove fatal for patients with weak immune systems).

In addition, private-equity business Carlyle Group recently announced the acquisition of Johnson & Johnson's (JNJ 0.22%) blood-testing business for around $4 billion. The deal is, of course, part of Johnson & Johnson’s divestment of divisions that it sees as offering less growth potential in future years, relative to some of its other divisions. Further divestment looks likely as the business seeks to restructure, so as to improve efficiency and deliver improved top- and bottom-line growth prospects.

So with 2014 still less than a month old, deal-making in the healthcare sector has been very much on the agenda. Although it has been a busy start to the year, there could be even more deals ahead, as the likes of AstraZeneca and Sanofi seek to combat their respective patent cliffs, with M&A activity being an obvious answer.

Furthermore, as Johnson & Johnson continues its divestments, this could mean increased activity, and when the low cost of borrowing is taken into account, 2014 could prove to be a year where the health-care sector goes all out on M&A activity.