8 Times the World Health Organization Declared a Public Health Emergency (Including for Mpox)

For the second time in three years, the World Health Organization (WHO) declared in August 2024 that mpox, formerly known as monkeypox, presented a “public health emergency of extraordinary concern,” or PHEIC. Although PHEICs may run the gamut from infectious disease to chemical or radioactive materials, all declarations of emergency since 2007 have been for viral diseases. The declaration was issued under the International Health Regulations, a legally binding agreement of 194 countries to help prevent and take measures to curb “extraordinary” public health risks with the potential for international spread.

Keep reading to learn more about the other PHEICs that have occurred over the past decade and a half.

H1N1 Influenza // 2009-2010

In April 2009, two kids in San Diego contracted a new strain of Influenza A; this particular H1N1 flu strain made the jump from pigs to humans in Mexico. Viral transmission from animals like pigs and birds to people isn’t unheard of, but when the same strain can then transmit from person to person, it’s a problem.

In this case, the virus was found to be a novel genetic remix of both swine and human flu viruses, although neither child had direct contact with pigs. Both patients recovered, but the virus showed resistance to two antiviral drugs, and by the end of that same month, the WHO declared the first PHEIC since the formation of the International Health Regulations in 2007.

One month after its detection in the U.S., H1N1 had mushroomed into 13,000 cases across 46 countries, thought to be accelerated by airline travel by infected passengers. By the end of the declaration, a little over a year later in August 2010, the WHO had confirmed over 18,000 global deaths related to the pandemic. Modeling puts the true number between 123,000 and 203,000, with the vast majority of deaths occurring in people under age 65 and in countries in the Americas. Although an effective vaccine was developed, it came about fairly late, after the peak of illness.

This outbreak marked the first time the malarial drug hydroxychloroquine was studied for flu prevention; the trial found it was not effective. This strain continues to circulate as a seasonal flu virus.

Poliomyelitis (Polio) // 2014-Ongoing

The 1950s U.S. polio outbreak, though not the first of its type, was the most feared. Scientists didn’t know much about the poliovirus then, and Americans blamed the disease on everything from insects and Italian immigrants to car exhaust and cats. One survey found that the only thing Americans feared more at the time was nuclear annihilation.

Although not nearly as deadly as portrayed, the virus is highly infectious. It enters through the mouth, replicates in the intestines, and can invade the nervous system, where it may cause paralysis. The iron lung, a negatively pressurized chamber developed to help patients breathe, became a symbol of the catastrophic effects of the disease. Jonas Salk’s injectable “dead virus” vaccine—the first of its kind—and later, Albert Sabin’s oral “live virus” vaccine, helped to eliminate polio on an international scale. Two of the three types of poliovirus were declared globally eradicated, but one strain continues to pop up in some Asian and African countries.

A PHEIC was declared in 2014, even though there were only 74 global cases at the time, the majority in Pakistan. Ten countries were considered to have active transmission of the virus and it was feared that with the increase in air travel, not implementing some coordinated effort would lead to continued spread. In July 2022, an unvaccinated man in New York was found to have polio, likely contracted from another person who had traveled abroad. The PHEIC remains active as of August 2024.

Western Africa Ebola // 2014-2016

The largest Ebola outbreak in history included 28,000 cases of the hemorrhagic fever and 11,310 deaths, a case-fatality rate of 40 percent. The death rate for health care and aid workers was particularly high. Believed to have originated in Guinea in January 2014, when an 18-month-old was infected by a bat, the virus circulated swiftly to neighboring Liberia and Sierra Leone thanks to poor public health infrastructure. Four months after the disease jumped borders and five months after it was first notified, the WHO declared a PHEIC in August 2014—a delay for which the WHO drew much criticism.

Through the education of local leaders about prevention programs and use of protective personal equipment (PPE), the virus was eventually stamped out. A first-of-its-kind clinical trial of an Ebola vaccine took place between August 2015 and January 2016. The drug had an estimated efficacy of 100 percent when given to primary and secondary contacts of confirmed Ebola patients.

Zika // 2016

In 2015, doctors in Brazil began noticing cases of microcephaly in infants. This birth defect is characterized by a smaller than normal head, a smaller and underdeveloped brain, and other neurological issues. The clusters of cases prompted a public health emergency declaration in early 2016. At the time, it was not known if the Zika virus was responsible, but these issues correlated with times and places of virus outbreaks.

Zika was the first arbovirus (virus transmitted by insects, which is this case are mosquitos in the Aedes genus) to cause a public health emergency of international concern. It doesn’t fit the profile of other similarly transmitted diseases, like dengue, which can lead to severe complications and death in infected people but rarely causes birth defects in babies. Zika seems to work in opposite fashion—causing mild or asymptomatic disease, but with the potential for devastating birth defects (collectively called congenital Zika syndrome). Infected people can also transmit the virus through sexual contact, which suggested that cases would spread beyond the range of the vector mosquitos. Within months, travelers disseminated the virus across more than 100 countries, including the U.S. A number of countries issued travel warnings and some went so far as to recommend delaying pregnancy.

The high incidence of infection in the Americas quickly led to herd immunity, and the outbreak subsided within the year.

Democratic Republic of Congo Ebola // 2019-2020

Ebola struck again, this time in the Democratic Republic of Congo. The WHO was first notified of cases on August 1, 2018. By the end of that year, it was the country’s largest outbreak of the disease and the world’s second largest Ebola outbreak after the West African epidemic a few years earlier. But it wasn’t declared a public health emergency until nearly a year later, in July 2019, when it reached Goma, a city with an international airport. During the outbreak, more than 3400 people were infected and 2000 of them died—a mortality rate of 66 percent.

This PHEIC was unprecedented because it occurred in a war zone. At least 70 Ebola patients and responders were injured and 11 were killed by armed groups’ targeted attacks.

However, this was the first time an Ebola vaccine (the same one studied in the West African Ebola epidemic) was available and administered widely from the start of the outbreak. And a clinical trial involving two antibody drugs showed significant reduction in deaths when given to patients shortly after hospitalization from the virus. Thanks to these breakthroughs, as well as extensive quarantine and isolation measures, this Ebola emergency was declared over in 2020.

COVID-19 // 2020-2023

A global nightmare that needs no introduction, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in a meat market in Wuhan, China, in December 2019. It is believed to be zoonotic, having jumped from animals to people who worked in the market.

A surprising feature of the virus is the numerous ways and varying intensities in which symptoms manifest (or fail to appear). Respiratory symptoms, blood clotting complications, loss of taste or smell, “covid-toes” (which swell and may turn red or purple), rashes, and cardiac and neurological complications are the most familiar. Or the virus may cause no symptoms at all.

On January 30, 2020, the WHO declared the novel coronavirus a public health emergency of international concern. In March 2020, the WHO declared a pandemic. As of July 2024, more than 775 million cases of COVID-19 have been reported worldwide and more than 7 million people have died of the disease. Millions more suffer from lingering symptoms of infection: using data from 2022, the National Academies of Sciences, Engineering, and Medicine estimate that as many as 19 million Americans have had or still have long COVID. The WHO ended the COVID-19 emergency on May 5, 2023, though the virus continues to circulate.

Mpox // 2022-2023

On July 24, 2022, the WHO declared an outbreak of mpox a PHEIC, citing its rapid spread across the globe. Although the disease is endemic in central Africa where small outbreaks occur, between June and July 2022, cases jumped from 3000 to 16,000 and the number of countries affected nearly doubled from 47 to 75.

The monkeypox virus is much less contagious than SARS-CoV-2 and is primarily transmitted through intimate touching and sex. It can also cling to used towels and bed sheets, making transmission among people in the same household possible. The disease is typically mild, though can be very painful and present as a fever and blistering rash. Nearly all of the initial cases in the 2022 outbreak emerged among men who have sex with men.

Citing control of transmission, the WHO ended the mpox PHEIC on May 11, 2023, though reports of cases continued to trickle in. As of August 2024, there have been 99,518 total cases across 122 countries and 207 total deaths worldwide.

Clade 1b Mpox // 2024-Ongoing

A different version of the mpox virus, called clade 1b, began spreading from the Democratic Republic of Congo to communities in Kenya, Rwanda, and Uganda for the first time earlier this year. More than 15,000 cases and 537 deaths have been reported in Congo so far, more than last year's total. Both of these factors prompted the WHO to declare another mpox public health emergency of international concern on August 14, 2024. At the time of the declaration, the outbreak had spread to 13 African countries, many of which had no prior history of cases.

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A version of this story was published in 2022; it has been updated for 2024.