In the event of a deadly disease outbreak, a group of World Health Organization (WHO) experts can declare a "public health emergency of international concern," or PHEIC, to trigger global action. Since the procedures to declare a PHEIC were implemented in 2005, the WHO has only done so six times. Let's take a look back at the prior instances.

In 2020, the WHO declared a global health emergency over a new coronavirus that originated in China but that spread to several countries across the world, including Germany. Officials said the declaration was due to "the potential for this virus to spread to countries with weaker health systems which are ill-prepared to deal with it."

It is estimated that the 2019 H1N1 influenza (also known as swine flu) pandemic, which began in Veracruz, Mexico, killed as many as 284,500 people. That's more than 15 times the original estimate of 18,500. The UK-based journal Lancet Infectious Diseases, however, has suggested that the true number of dead could have ultimately been as high as 579,000. Here, a Chinese medic prepares a vaccination.

The outbreak of the Ebola virus in Sierra Leone, Guinea and Liberia between 2013 and 2016 was deadlier than all other Ebola outbreaks combined, killing at least 11,300 people. A 2018 study by the Oxford-based Journal of Infectious Diseases estimated the outbreak cost the three countries involved as much as $53 billion (€48 billion).

In 2014, Pakistan's failure to curb the spread of polio prompted the WHO to declare the disease's resurgence a PHEIC. The warning covered Pakistan, Syria and Cameroon. At the time, Pakistan accounted for more than one-fifth of the world's 417 reported cases.

In 2016, the Zika virus was declared a PHEIC by the WHO. The outbreak was identified in Brazil in 2015. Ultimately, the disease spread to 60 countries, with 2,300 confirmed cases of microcephaly among newborns. Microcephaly causes birth defects such as abnormally small heads, which can lead to developmental problems.

In July 2019, after its fourth meeting since the DRC's outbreak began, the WHO Emergency Committee on Ebola declared it a PHEIC. As of January 14, 2020, the WHO had confirmed 3,406 cases of Ebola in the DRC, including some 2,236 deaths since the outbreak began in August 2018. The WHO estimates the disease could cost the DRC as much as $1 billion (€900,000 million).

On December 31, 2019, China notifies the World Health Organization of a string of respiratory infections in the city of Wuhan, home to some 11 million people. The root virus is unknown and disease experts around the world begin working to identify it. The strain is traced to a seafood market in the city, which is quickly shut down. Some 40 people are initially reported to be infected.

On January 11, China announces the first death from the coronavirus — a 61-year-old man, who had shopped at the Wuhan market, dies from complications with pneumonia. Like SARS and the common cold, scientists identified that the new virus is in the coronavirus family. It is temporarily named 2019-nCoV. Symptoms include fever, coughing, difficulty breathing, and pneumonia.

In the following days, countries such as Thailand and Japan begin to report cases of infections in people who had visited the same Wuhan market. In China, a second fatality is confirmed in the city. By January 20, three people have died in China and more than 200 are infected.

China places Wuhan on quarantine on January 23 in an attempt to limit the spread of the virus. Transportation is suspended and workers attempt to quickly build a new hospital to treat infected patients, which total over 830 by January 24, as the death toll climbs to 26. Officials eventually extend the lockdown to 13 other cities, affecting at least 36 million people.

More and more cases are confirmed outside of China, including in South Korea, the US, Nepal, Thailand, Hong Kong, Singapore, Malaysia and Taiwan. As the number of infections rises, the World Health Organization on January 23 determines that it's "too early" to declare a global public health emergency.

On January 24, French authorities confirm three cases of the new coronavirus within its borders, marking the disease's first appearance in Europe. Hours later, Australia confirms four people have been infected with the respiratory virus.

On January 27, Germany announces its first known case of the virus — a 33-year-old in Bavaria who contracted it during a workplace training with a visiting Chinese colleague. He is put under quarantine and observation at a Munich hospital. The following day, three of his colleagues are confirmed infected. The death toll in China reaches 132, with around 6,000 infected worldwide.

On January 30, the UN's World Health Organization (WHO) declares coronavirus a public health emergency of international concern in a bid to protect countries with "weaker health systems." However, WHO Secretary-General Tedros Adhanom Ghebreyesus does not recommend trade and travel restrictions, saying these would be "an unnecessary disruption."

The first death linked to the novel coronavirus outside of China is reported in the Philippines on February 2. A 44-year-old Chinese man had traveled from Wuhan to Manila before falling ill and being taken to hospital, where he later died of pneumonia.

Also on February 3, the cruise ship Diamond Princess is quarantined off Yokohama in Japan after cases of the new coronavirus were found on board. As of February 17, the number of people infected has grown to more than 450, the largest cluster of cases outside of China. Several of the 3,700 passengers and crew onboard the ship are being or have been flown back to their home countries.

Cases in Italy rise dramatically, with 77 deaths and thousands of confirmed cases by March 3. Many countries instigate travel restrictions to northern Italy and tourist numbers plummet. On March 8, the Italian government put the entire Lombardy region into quarantine, affecting 16 million people. March 10 sees 168 fatalities in Italy, the highest in a single day.

European and US stock markets slump on March 6, leading to the worst week since the 2008 financial crisis. The effect on global business has been significant, with many companies reporting losses and the tourism industry and airlines badly hit. The EU pledge €7.5 billion ($8.4 billion) on March 10 in an investment fund to try to stop the Eurozone falling into a recession.

As worldwide cases top 127,000 and deaths pass 4,700, the World Health Organization designates the global outbreak as a "pandemic" on March 11. US President Donald Trump announces a travel restriction on people coming from the Schengen Zone in Europe, annoying the EU. German Chancellor Angela Merkel announces that in Germany, 70% of the population could get the virus.

On March 14, Spain joins Italy in imposing a near-total nationwide lockdown to prevent the virus spreading. The population of 46 million is told not to leave their homes unless for essential tasks. In France, cafés, restaurants and non-essential shops are closed as of March 15. Many public events in Germany are cancelled and schools close.

As of March 15, many countries impose strict travel bans or restrictions in an attempt to stop the spread of Covid-19. For example, New Zealand and Australia require all international passengers to self-isolate for 14 days after arrival in the country. The US extends a European travel ban to include the United Kingdom and Ireland.

In a landmark televised address German Chancellor Angela Merkel announces far-reaching restrictions on everyday life on March 22, banning meetings between more than two people not from the same household outside of the workplace. The country has a surprisingly low death rate, a phenomenon attributed to a high level of testing, and a high number of intensive care beds.

On March 23rd Britain becomes the latest country to impose restrictions on personal freedoms, with people only allowed to leave their homes in a limited number of circumstances. Prime Minister Boris Johnson is diagnosed with the viruson March 27, as well as heir to the throne Prince Charles on March 25. Meanwhile, there are complaints that not everyone is taking social distancing seriously.

On March 27 the US overtakes China in terms of the number of people infected, making it the country with the most cases of COVID-19. This came as President Donald Trump claimed that the nation would get back to work "pretty quickly." At the same time, it emerged that more than 3 million Americans had lost their jobs due to the pandemic. New York is worst-hit, with a hospital ship sent to help out.

Spain also overtakes China in the number of COVID-19 cases on March 30, as the government toughens the severity of its lockdown. All non-essential activities are halted. Only Italy has a higher death toll than Spain. Most affected is the capital, Madrid. With funeral services overwhelmed, officials turn the Palacio de Hielo ice skating rink into a temporary morgue.

On April 2nd the Johns Hopkins University announced on Thursday that there were more than a million confirmed coronavirus cases around the world. The US is the most affected with three times the number than China, where the virus emerged in December. Over 50.000 people have died — and the outlook remains grim.

The 55-year-old was admitted to the intensive care unit at London's St Thomas hospital on Monday evening (6.4.) and was given oxygen treatment after his condition worsened. He had been diagnosed with COVID-19 on March 27.