Coronavirus: Timeline of pandemics and other viruses that humans caught by interacting with animals

Stop the Wildlife Trade: From 1918 to today, the deadly diseases that have become more frequent

Viruses that jump from animals to humans, known as zoonoses, have existed for centuries, but experts say outbreaks of dangerous new diseases with the potential to become pandemics are on the rise. Indeed, they have become four times as frequent in the past half-century.

Since the 1970s, it is estimated at least three dozen infectious diseases have emerged from human interference with animals, including Sars, Mers, Ebola, bird flu, swine flu and the Zika virus. As far back as 2007 the World Health Organisation warned that infectious diseases were emerging at a rate that had not been seen before.

The spread of the viruses is put down to a deadly combination of wildlife trafficking and consumption, increasing human encroachment into wildlife habitats as more people live in densely populated areas – and air travel, which enables pathogens to take hold globally.

Three years ago, an article published by the US National Centre for Biotechnology Information stated, presciently: “The Aids and influenza pandemics have claimed and will continue to claim millions of lives. The recent Sars and Ebola epidemics have threatened populations across borders. The emergence of Mers may well be warning signals of a nascent pandemic threat.”

Zoonotic diseases are complex, and it’s sometimes impossible to say a virus has disappeared, because it might have many different strains, and might mutate and lie dormant. This is a timeline of the main zoonotic diseases to have hit us since the start of the 20th century:

The 1918 flu pandemic: This was the most severe pandemic in modern times, killing at least 50 million people in two years. It is widely believed that the virus originated in birds because it shared genetic mutations with the bird flu virus later found in Asia, and could have transferred to horses in the trenches of the first world war before spreading to humans. This is disputed, with one study suggesting it came from mammals.

Asian flu, 1957: In February 1957, a new influenza virus, known as H2N2 emerged in east Asia, which spread into a pandemic. It originated from an avian influenza virus, causing an estimated 1.1 million deaths worldwide.

HIV: First identified in 1981, the disease is thought to have been acquired by people in central Africa hunting chimpanzees and coming into contact with their infected blood. However, studies show that HIV may have jumped from apes to humans as far back as the late 1800s, and it has existed in the West since at least the mid to late 1970s. HIV has killed about 35 million people to date, according to the World Health Organisation.

Sars: Severe acute respiratory syndrome is another type of coronavirus, which killed at least 770 people globally in an epidemic in 2002-3. Most victims were in southern China, Vietnam and Singapore. Scientists are not certain of its origins but like Covid-19 it’s thought it could have come from bats and spread to other animals such as civet cats, which are commonly sold in squalid conditions in street markets. The epidemic resulted in more than 8,000 cases, in 26 countries. Of those, 774 died.

Swine flu: In 2009-2010 a new strain of flu emerged in pigs in Mexico. The H1N1 virus killed nearly tens of thousands of people in a global pandemic that spread to 214 countries in less than a year. However, overall the outbreak was not as serious as originally predicted, largely because many older people were already immune to it. And the NHS says it now circulates each year and is considered a normal seasonal flu strain, which is covered by the annual seasonal flu vaccine. A study in 2013 suggested between 123,000 and 200,000 people globally may have died as a result of the 2009 H1N1 pandemic.

Mers: First identified in Saudi Arabia in 2012, Middle East respiratory syndrome is also a coronavirus whose symptoms include fever, cough and shortness of breath. With an estimated death rate of 35 per cent, the disease has killed 858 people, according to the WHO. Again, scientists think it spread to humans from bats, this time via camels.

Ebola: A 2014–2016 outbreak in West Africa was the largest and most complex Ebola outbreak since the virus was first discovered in 1976, killing 11,300 people. Scientists say it began with a child in Guinea who came into contact with infected bats, but it has since been widely linked to the killing and butchering of bush meat, including monkeys, chimps, antelopes, fruit bats, porcupines and rats.

Zika: First identified in Uganda in 1947 in monkeys, the mosquito-borne virus caused alarm in 2015, when it was thought to be the cause of thousands of cases of microcephaly – a shorter-than-normal head – in babies in Brazil. Outbreaks soon appeared throughout the Americas, Africa and other regions. It was thought to have killed 29 babies.

Bird flu: Avian influenza, also called avian flu or bird flu, has many different strains but one of those, H7N9, has caused 1,568 cases in humans and 616 deaths worldwide since 2013, according to the Food and Agriculture Organisation of the United Nations.

Another strain of the virus, H5N1, first identified in 1997, spread across east and southeast Asia, killing six people in Hong Kong and leading to vast swathes of chickens and turkeys – from Hong Kong to Britain – having to be culled early after contracting the disease. To date 861 cases of human H5N1 infection and 455 deaths have been reported. The highest number of infections and deaths were in Indonesia, Vietnam and Thailand. The H5N1 virus, which has a 60 per cent mortality rate among infected humans, according to WHO, has not gone away, but is thought to have mutated.

Bird flu has been linked to rapid intensification of the poultry industry, with thousands of birds crowded together indoors and with compromised immune systems.

The Independent is campaigning against the wildlife trade at the core of the Covid-19 pandemic.