The World Health Organization on Saturday declared the monkeypox outbreak, which has affected nearly 17,000 people in 74 countries, to be a global health emergency -- the highest alarm it can sound.

"I have decided that the global monkeypox outbreak represents a public health emergency of international concern," WHO chief Tedros Adhanom Ghebreyesus said at a press conference.

He said a committee of experts who met on Thursday was unable to reach a consensus, so it fell to him to decide whether to trigger the highest alert possible.

"WHO's assessment is that the risk of monkeypox is moderate globally and in all regions, except in the European region where we assess the risk as high," he added.

Monkeypox has affected more than 16,800 people in 74 countries, according to a tally by the US Centers for Disease Control and Prevention (CDC) published on July 22.

Washington welcomed the WHO's declaration as "a call to action for the world community to stop the spread of this virus".

"A coordinated, international response is essential to stop the spread of monkeypox, protect communities at greatest risk of contracting the disease, and combat the current outbreak," said Raj Panjabi, senior director for the White House's global health security and biodefence division.

A surge in monkeypox infections has been reported since early May outside the West and Central African countries where the disease has long been endemic.

Overall, 98 percent of infected people were gay or bisexual men, and around a third were known to have visited sex-on-site venues such as sex parties or saunas within the previous month.

Tedros has previously expressed concern that stigma and scapegoating could make the outbreak harder to track.

On Saturday, he said the outbreak was "concentrated among men who have sex with men, especially those with multiple sexual partners" which meant it "can be stopped with the right strategies in the right groups".

He urged all countries to "work closely with communities of men who have sex with men, to design and deliver effective information and services, and to adopt measures that protect" the communities affected.

- Potential vaccine -

On June 23, the WHO convened an emergency committee of experts to decide if monkeypox constitutes a so-called Public Health Emergency of International Concern -- the UN health agency's highest alert level. 

But a majority advised Tedros that the situation, at that point, had not met the threshold.

The second meeting was called on Thursday with case numbers rising further, where Tedros said he was worried.

"I need your advice in assessing the immediate and mid-term public health implications," Tedros told the meeting, which lasted more than six hours.

A viral infection resembling smallpox and first detected in humans in 1970, monkeypox is less dangerous and contagious than smallpox, which was eradicated in 1980.

Ninety-five percent of cases have been transmitted through sexual activity, according to a study of 528 people in 16 countries published in the New England Journal of Medicine -- the largest research to date.

The European Union's drug watchdog on Friday recommended for approval the use of Imvanex, a smallpox vaccine, to treat monkeypox.

Imvanex, developed by Danish drugmaker Bavarian Nordic, has been approved in the EU since 2013 for the prevention of smallpox. 

It was also considered a potential vaccine for monkeypox because of the similarity between the monkeypox virus and the smallpox virus.  

The first symptoms of monkeypox are fever, headaches, muscle pain and back pain during the course of five days. 

Rashes subsequently appear on the face, palms of hands and soles of the feet, followed by lesions, spots and finally scabs.

From beginnings in Africa to global spread

As monkeypox infections jump around the world, prompting a scramble for vaccines, AFP looks at how the disease has spread since first appearing in Africa in the 1970s.

The World Health Organization on Saturday declared the outbreak, which has affected nearly 16,000 people in 72 countries, to be a global health emergency -- the highest alarm it can sound.

Monkeypox, so called because it was first discovered in a monkey, is related to the deadly smallpox virus, which was eradicated in 1980, but is far less severe. 

The strain currently circulating outside Africa is the milder of two known versions.

- 1970: First case in humans -

Human monkeypox is first identified in 1970 in Zaire (now the Democratic Republic of Congo) in a nine-year-old boy.

It becomes endemic in the tropical rainforests of central and west Africa, where 11 countries report cases.

The virus is transmitted through close contact with infected animals, mostly rodents, or humans.

- 2003: First outbreak outside Africa -

In June 2003, the disease surfaces in the United States -- the first time it had been detected outside Africa.

The illness is believed to have spread after rodents, imported into the US from Ghana, infected prairie dogs.

The US Centers for Disease Control and Prevention (CDC) reports 87 cases but no fatalities.

- 2017: Epidemic in Nigeria -

2017 brings a major outbreak in Nigeria, with more than 200 confirmed cases and a fatality rate of around three percent, according to the WHO. 

Over the next five years, sporadic cases are reported around the world in travellers arriving from Nigeria, notably in Britain, Israel, Singapore and the United States.

- May 2022: Surge outside Africa -

In May 2022, a flurry of cases is detected in countries outside Africa, in people with no travel links to the region. Most of those affected are gay men.

Europe is the epicentre of the new outbreak.

By May 20, Britain has recorded 20 cases, mostly among gay men.

On the same date, the WHO counts 80 confirmed cases around the world, including in Australia, Belgium, Canada, France, Germany, Italy, Portugal, Spain and Sweden.

- Late May: Vaccinations start -

On May 23, the United States says it is preparing to administer smallpox vaccines, which are effective against monkeypox, to people who have been in close contact with monkeypox patients.

Three days later, the European Union says it is working on centralising purchases of vaccines, as it did for Covid-19.

- June: More than 1,000 cases -

In early June, WHO chief Tedros Adhanom Ghebreyesus says that more than 1,000 confirmed cases of monkeypox have been reported to WHO from 29 countries where the virus is not usually present.

On June 21, Britain announces plans to offer vaccines to gay and bisexual men with multiple sexual partners.

WHO experts meet on June 23 to discuss the threat but decide that monkeypox does not constitute a global public health emergency.

- July: 14,000 cases, 70 countries -

On July 8, health authorities in France also launches pre-emptive jabs for people considered at risk, including gay men, trans people and sex workers.

On July 14, the US CDC reports more than 11,000 confirmed cases in some 60 countries where monkeypox is not usually found. Most of the cases are in Europe, the United States and Canada.

The number of infections in New York doubles in under a week to several hundred. People stand in line for vaccines, which are in short supply. 

On July 20, Tedros announces that almost 14,000 confirmed cases have been reported to the WHO this year, from more than 70 countries, with five deaths, all in Africa.

He says six countries reported their first cases in the previous week, while some states have limited access to diagnostics and vaccines, making the outbreak harder to track and to stop. 

The WHO calls a new expert meeting for July 21 to decide whether to declare a global health emergency.

On Saturday, Tedros announces the monkeypox outbreak to be a "public health emergency of international concern".

How a global health emergency is decided

A Public Health Emergency of International Concern (PHEIC) is the rarely used top alert available to the World Health Organization to tackle a global disease outbreak.

The WHO on Saturday declared the surge in monkeypox to be a PHEIC after experts reviewed the situation at an emergency committee meeting two days earlier.

Here is a look at how the decision is made and previous PHEIC declarations:

- What is a PHEIC? -

The conditions which must be met are set out under the 2005 International Health Regulations (IHR) -- the legal framework defining countries' rights and obligations in handling public health events that could cross borders.

A PHEIC is defined in the regulations as "an extraordinary event which is determined to constitute a public health risk to other states through the international spread of disease and to potentially require a coordinated international response".

The definition implies that the situation is serious, sudden, unusual or unexpected, carries implications for public health beyond an affected country's border, and may require immediate international action.

- Emergency committee -

The WHO's 16-member emergency committee on monkeypox is chaired by Jean-Marie Okwo-Bele from the Democratic Republic of Congo, who is a former director of the WHO's Vaccines and Immunisation Department.

The committee brings together virologists, vaccinologists, epidemiologists and experts in the fight against major diseases. 

It is co-chaired by Nicola Low, an associate professor of epidemiology and public health medicine from Bern University.

The other 14 members are from institutions in Brazil, Britain, Japan, Morocco, Nigeria, Russia, Senegal, Switzerland, Thailand and the United States.

Eight advisers from Canada, the DRC, South Africa, Sweden, Switzerland and the United States also take part in the meetings.

- Decision -

The emergency committee provided WHO chief Tedros Adhanom Ghebreyesus with an assessment of the risk to human health, the risk of international spread and the risk of interference with international traffic.

But it was unable to reach a consensus on whether or not to trigger the highest alert, Tedros said Saturday, so the WHO chief then had to decide himself.

- Six previous PHEICS -

The WHO has previously declared a PHEIC six times:

-- 2009: H1N1 swine flu

The pandemic was first detected in Mexico and then quickly spread across the United States and the rest of the world.

-- May 2014: Poliovirus

Declared following a rise in cases of wild polio and circulating vaccine-derived poliovirus. Besides Covid, it is the only PHEIC still in place.

-- August 2014: Ebola

Outbreak in western Africa which spread to Europe and the United States.

-- February 2016: Zika virus

The epidemic began in Brazil and heavily affected the Americas. The only PHEIC declared over a mosquito-borne virus.

-- July 2019: Ebola

The second Ebola PHEIC was over the outbreak in Kivu in eastern DRC.

-- January 2020: Covid-19

Declared when -- outside of China where the virus first emerged -- there were fewer than 100 cases and no deaths.

- Covid-19 frustrations -

The Covid-19 PHEIC declaration came after a third meeting of the emergency committee on the spreading virus. Meetings on January 22 and 23, 2020 decided that the outbreak did not constitute a PHEIC.

Despite the declaration, it was only after March 11, that Tedros described the rapidly worsening situation as a pandemic, leading many countries to wake up to the danger.

The sluggish global response still rankles at the WHO's headquarters and raised questions about whether the PHEIC system under IHR was fit for purpose.

By March 11, the number of cases outside China had soared, with more than 118,000 people having caught the disease in 114 countries, and 4,291 people having lost their lives, following a jump in deaths in Italy and Iran.

"The warning in January was way more important than the announcement in March," WHO emergencies director Michael Ryan said on the second anniversary of the pandemic declaration.

"People weren't listening. We were ringing the bell and people weren't acting.