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H1N1 Influenza: 2009-2010 -

In April 2009, two children in San Diego contracted a new strain of Influenza A, which made the jump from pigs to humans in Mexico. Although viral transmission from animals to people isn't unheard of, it becomes a problem when the same strain is transmitted from person to person. 

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H1N1 Influenza: 2009-2010 -

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. 

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H1N1 Influenza: 2009-2010 -

Both patients recovered, but the virus showed resistance to two antiviral drugs. By the end of that same month, the WHO declared the first public health emergency since the formation of the International Health Regulations in 2007.

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H1N1 Influenza: 2009-2010 -

One month after its detection in the US, there were 13,000 cases across 46 countries, believed to be accelerated by airline travel. An estimated 123,000 to 203,000 people died from H1N1 Influenza. Although an effective vaccine was developed, it came about fairly late after the peak of illness.

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Poliomyelitis (polio): 2014-ongoing -

The WHO declared polio a public health emergency in 2014, even though there were only 74 global cases at the time. 

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Poliomyelitis (polio): 2014-ongoing -

Ten countries were considered to have active transmission of the virus, and it was feared that it would spread with air travel. 

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Poliomyelitis (polio): 2014-ongoing -

In July 2022, an unvaccinated man in New York was found to have polio, likely contracted from another person who had traveled abroad. The public health emergency by the WHO remains active as of August 2024.

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Western Africa Ebola: 2014-2016 -

The largest Ebola outbreak in history included 28,000 cases and 11,310 deaths, a case-fatality rate of 40%. The death rate for health care and aid workers was particularly high.

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Western Africa Ebola: 2014-2016 -

Believed to have originated in Guinea in January 2014, the virus circulated swiftly to neighboring Liberia and Sierra Leon. The WHO declared it a public health emergency five months after it was first notified, a delay which drew much criticism.

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Western Africa Ebola: 2014-2016 -

Through education about prevention programs and the use of protective personal equipment (PPE), the virus was eventually stamped out.

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Western Africa Ebola: 2014-2016 -

A clinical trial of an Ebola vaccine took place between August 2015 and January 2016. The drug had an estimated efficacy of 100% when given to primary and secondary contacts of confirmed Ebola patients.

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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. 

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Zika: 2016 -

The number of cases prompted a public health emergency declaration in early 2016. At the time, it wasn't known if the Zika virus was responsible, but these issues correlated with times and places of virus outbreaks.

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Zika: 2016 -

Zika was the first arbovirus, a virus transmitted by insects (in this case mosquitos in the Aedes genus), to cause an international public health emergency. 

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Zika: 2016 -

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

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Democratic Republic of Congo Ebola: 2019-2020 -

Ebola struck again, this time in the Democratic Republic of Congo (DRC). 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 since the Ebola West African outbreak a few years earlier.

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Democratic Republic of Congo Ebola: 2019-2020 -

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. This outbreak occurred in a war zone and at least 70 Ebola patients and responders were injured. Eleven were killed in targeted attacks by armed groups.

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Democratic Republic of Congo Ebola: 2019-2020 -

However, this was the first time an Ebola vaccine was available and administered widely from the start of the outbreak. Thanks to the vaccine, as well as extensive quarantine and isolation measures, this Ebola emergency was declared over in 2020.

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COVID-19: 2020-2023 -

A severe acute respiratory syndrome that doesn't need much introduction, the coronavirus emerged in a meat market in Wuhan, China, in December 2019. It's believed to be zoonotic, having jumped from animals to people in the market.

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COVID-19: 2020-2023 -

A surprising feature of the virus is the numerous ways and varying intensities in which symptoms manifest. Respiratory symptoms, blood clotting complications, and loss of taste or smell are the most common. In some cases, the virus may cause no symptoms at all.

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COVID-19: 2020-2023 -

On January 30, 2020, the WHO declared the coronavirus a public health emergency of international concern. In March 2020, the WHO declared a pandemic.

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COVID-19: 2020-2023 -

As of July 2024, more than 775 million cases of COVID-19 have been reported worldwide and more than seven million people have died of the disease. The WHO ended the COVID-19 emergency on May 5, 2023, though the virus continues to circulate.

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Mpox: 2022-2023 -

On July 24, 2022, the WHO declared an outbreak of mpox a public health emergency, citing its rapid spread across the globe. 

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Mpox: 2022-2023 -

Although the disease is endemic in central Africa where small outbreaks occur, between June and July 2022, cases jumped from 3,000 to 16,000 in 75 countries.

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Mpox: 2022-2023 -

Less contagious than SARS-CoV-2, mpox is primarily transmitted through intimate touch and sex. It can also cling to used towels and bed sheets, making transmission among people in the same household possible. Symptoms are typically mild, though can be very painful and present as a fever and blistering rash.

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Mpox: 2022-2023 -

Citing control of transmission, the WHO ended the mpox emergency on May 11, 2023. As of August 2024, there have been 99,518 total cases across 122 countries and 207 total deaths worldwide.

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Clade 1b Mpox: 2024-ongoing -

A different version of the mpox virus, called clade 1b, began spreading from the DRC to Kenya, Rwanda, and Uganda in 2024.  

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Clade 1b Mpox: 2024-ongoing -

Over 15,000 cases have been reported in the DRC so far, which prompted the WHO to declare another mpox public health emergency on August 14, 2024. 

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Clade 1b Mpox: 2024-ongoing -

There is now an ongoing global outbreak of clade II mpox, which has caused more than 100,000 cases in 122 countries. This includes 115 countries where mpox was not previously reported. The outbreak is attributed to subclade IIb, according to the CDC.

Sources: (World Health Organization) (Mental Floss) (BBC)

See also: Long before COVID: The deadliest pandemics in history

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