Washington (CNN) States of emergency are nothing new for the United States.

There are currently 28 concurrent active national emergencies in America -- there's been at least one national emergency for nearly four decades straight.

The opioid crisis, however, will not technically be added to the list because the White House determined it is more appropriately deemed a public health emergency.

President Donald Trump's declaration on the opioid crisis on Thursday constitutes a public health emergency — not a full-blown national emergency under the National Emergencies Act or Stafford Act, which would have had wider-reaching powers. Trump's designation for opioids is a separate emergency focused on the Health and Human Services Department.

That determination was not criticized by public health officials contacted by CNN who worked in previous administrations.

Public health emergencies are often declared in the aftermath of a natural disaster like a hurricane or after a disease outbreak. A public health emergency has already been declared 15 times in 2017 , including multiple times, usually for individual states, after Hurricanes Harvey, Irma, Maria and Nate. HHS also used the public health emergency designation in 2017 after the California wildfires and renewed designations having to do with Zika virus.

The President's opioid panel recommended both options -- public health emergency and national emergency -- as possible paths forward for Trump. Trump had signaled in August that he intended to declare a national emergency.

"The opioid crisis is an emergency, and I am saying, officially, right now, it is an emergency. It's a national emergency," Trump said in August. "We're going to spend a lot of time, a lot of effort and a lot of money on the opioid crisis. It is a serious problem the likes of which we have never had."

A senior White House official told CNN on Thursday that the declaration would be made under the Public Health Services Act, saying a full-blown national emergency would have opened the door to unnecessary funding that is intended for the immediate aftermath of disasters.

The rapid increase in the number of drug-related deaths over the last two decades prompted Trump's comments in August and much discussion during the 2016 campaign.

More than two dozen national emergencies are already in effect from past presidents, many of them already renewed by Trump.

This is according to a CNN analysis of data from the Congressional Research Service, the Federal Register and the White House.

Declaring a national state of emergency under the National Emergencies Act of 1974 outlines how a president can activate special statutory power during a crisis.

George W. Bush declared 13 emergencies and Barack Obama declared 12 -- nearly all of which are still active today. Bill Clinton declared 17 national emergencies, six of which are still active. Ronald Reagan declared six and George H.W. Bush declared four -- but all of those have been revoked by now.

The first declaration under the National Emergencies Act of 1974 came during the Iran hostage crisis -- a national emergency that is still active today. Jimmy Carter blocked Iranian government property from entering the country. It's been renewed each year by all presidents since then.

Presidents must renew national emergencies every year because the statute lets emergencies automatically expire after one year.

A special White House panel led by New Jersey Republican Gov. Chris Christie recommended that Trump make an emergency declaration on opioids. A statement from the White House in August said Trump has "instructed his Administration to use all appropriate emergency and other authorities to respond to the crisis caused by the opioid epidemic."

Other ongoing national emergencies focus on the 9/11 terror attacks, the war in Iraq and the blocking of some property and people from around the world in countries such as Yemen, Ukraine, South Sudan, Venezuela and Burundi.

Past emergencies have focused on everything from swine flu to rough diamonds.

Here's a list of the 28 active national emergencies:

1. Blocking Iranian Government Property (Nov. 14, 1979)

2. Proliferation of Weapons of Mass Destruction (Nov. 14, 1994)

3. Prohibiting Transactions with Terrorists Who Threaten to Disrupt the Middle East Peace Process (Jan. 23, 1995)

4. Prohibiting Certain Transactions with Respect to the Development of Iranian Petroleum Resources (Mar. 15, 1995)

5. Blocking Assets and Prohibiting Transactions with Significant Narcotics Traffickers (Oct. 21, 1995)

6. Regulations of the Anchorage and Movement of Vessels with Respect to Cuba (Mar. 1, 1996)

7. Blocking Sudanese Government Property and Prohibiting Transactions with Sudan (Nov. 3, 1997)

8. Blocking Property of Persons Who Threaten International Stabilization Efforts in the Western Balkans (Jun. 26, 2001)

9. Continuation of Export Control Regulations (Aug. 17, 2001)

10. Declaration of National Emergency by Reason of Certain Terrorist Attacks (Sept. 14, 2001)

11. Blocking Property and Prohibiting Transactions with Persons who Commit, Threaten to Commit, or Support Terrorism (Sept. 23, 2001)

12. Blocking Property of Persons Undermining Democratic Processes or Institutions in Zimbabwe (Mar. 6, 2003)

13. Protecting the Development Fund for Iraq and Certain Other Property in Which Iraq has an Interest (May 22, 2003)

14. Blocking Property of Certain Persons and Prohibiting the Export of Certain Goods to Syria (May 11, 2004)

15. Blocking Property of Certain Persons Undermining Democratic Processes or Institutions in Belarus (Jun. 16, 2006)

16. Blocking Property of Certain Persons Contributing to the Conflict in the Democratic Republic of the Congo (Oct. 27, 2006)

17. Blocking Property of Persons Undermining the Sovereignty of Lebanon or Its Democratic Processes and Institutions (Aug. 1, 2007)

18. Continuing Certain Restrictions with Respect to North Korea and North Korean Nationals (Jun. 26, 2008)

19. Blocking Property of Certain Persons Contributing to the Conflict in Somalia (Apr. 12, 2010)

20. Blocking Property and Prohibiting Certain Transactions Related to Libya (Feb. 25, 2011)

21. Blocking Property of Transnational Criminal Organizations (Jul. 25, 2011)

22. Blocking Property of Persons Threatening the Peace, Security, or Stability of Yemen (May 16, 2012)

23. Blocking Property of Certain Persons Contributing to the Situation in Ukraine (Mar. 6, 2014)

24. Blocking Property of Certain Persons With Respect to South Sudan (Apr. 3, 2014)

25. Blocking Property of Certain Persons Contributing to the Conflict in the Central African Republic (May 12, 2014)

26. Blocking Property and Suspending Entry of Certain Persons Contributing to the Situation in Venezuela (Mar. 9, 2015)

27. Blocking the Property of Certain Persons Engaging in Significant Malicious Cyber-Enabled Activities (Apr. 1, 2015)

28. Blocking Property of Certain Persons Contributing to the Situation in Burundi (Nov. 23, 2015)