• Mpox is a viral infection which spreads through close contact, including sexual contact.
• It causes flu-like symptoms, including fever, chills and muscle aches, as well as lesions filled with pus.
• A new offshoot of clade 1, known as clade 1b, is said to be responsible for the recent uptick in cases, according to the WHO.

The World Health Organization has declared mpox a global public health emergency for the second time in two years, following the spread of an outbreak in the Democratic Republic of Congo to neighboring countries.

New cases of the virus have since been been identified outside of the continent, in countries including Thailand, Philippines, Sweden and Pakistan.

Health officials are raising concerns because many of the new cases in Africa have been identified as a new and deadlier strain, known as clade 1b. The new strain has also been confirmed outside of the continent, in Thailand.

CNBC breaks down what we know so far.

What is mpox?

Mpox is a viral infection that spreads through close contact, including sexual contact. It causes flu-like symptoms, including fever, chills and muscle aches, as well as lesions filled with pus. While usually mild, it can be fatal.

There are broadly two types of of mpox, known as clades, with the latest outbreak identified as clade 1. The current strain appears to spread more easily and has a higher fatality rate when compared with the 2022 strain known as clade 2.

It also appears to disproportionately affect young people, with most deaths occurring among children.

Why are cases rising?

A new offshoot of clade 1, known as clade 1b, is said to be responsible for the recent uptick in cases, according to the WHO.

The WHO said that clade 1b is spreading person to person, often through sexual contact. While first identified in 2024, it is thought to have emerged in the DRC around 2023.

"The outbreak associated with clade Ib in the DRC primarily affects adults and is spreading rapidly, sustained largely, but not exclusively, through transmission linked to sexual contact and amplified in networks associated with commercial sex and sex workers," the health organization said in a statement on Aug. 19.

Where are the cases?

Alongside the DRC, cases of clade 1b have been identified in Burundi, Kenya, Rwanda, Uganda and Thailand.

Cases of clade 1 have been reported in the Central African Republic, the Republic of Congo and Sweden.

Cases linked to the milder clade 2 have been reported in Cameroon, Côte d'Ivoire, Liberia, Nigeria, South Africa, the Philippines and Pakistan.

What does the WHO declaration mean?

The "public health emergency of international concern" status is the WHO's highest designation and aims to accelerate international public health measures and cooperation to contain a disease.

"It's clear that a coordinated international response is essential to stop these outbreaks and save lives," said WHO Director-General Tedros Adhanom Ghebreyesus when the declaration was made on Aug. 14.

"The detection and rapid spread of a new clade of mpox in eastern DRC, its detection in neighbouring countries that had not previously reported mpox, and the potential for further spread within Africa and beyond is very worrying," he added.

However, Dr. Hans Kluge, the WHO's regional director for Europe, stressed last week that Mpox is "not the new Covid."

In a statement published Tuesday, Kluge rejected comparisons between mpox and the coronavirus pandemic and said the risk to the general population is low.

"We can, and must, tackle mpox together — across regions and continents," Kluge said.

What are authorities doing?

There are vaccines to treat the virus, though access is an issue. The WHO is now working with countries and vaccine manufacturers to increase access for affected countries.

The U.N. health agency said it has so far released $1.45 million in contingency funds and might need to release more in the coming days. It expects an immediate funding requirement of an initial $15 million will be needed for its response plan.

The Africa Centres for Disease Control and Prevention (Africa CDC) has struck a partnership with vaccine maker Bavarian Nordic, which it said would help deliver 2 million doses this year in addition to existing, and 10 million by the end of 2025.

Bavarian Nordic said it is also supplying vaccines to countries outside of Africa, and that it is seeking approval from the European Union's drug regulator to extend the use of its mpox vaccine for teenagers.