Thursday, February 9, 2023

How Do Pandemics End?

By Dilip Bobb

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Every single person on the planet experiencing various stages of lockdown and facing the greatest threat to their lives in living memory, must be asking one panic-stricken question. How do pandemics end? The truth is that history has no easy answers.

The closest virus strain to Covid-19 was SARS (Severe Acute Respiratory Syndrome). Like Covid-19, it originated in China and was believed to have been transmitted by animals, possibly bats, spread to other animals (civet cats) and then infected humans in the Guangdong province of southern China in 2002-2003. The SARS epidemic was more restricted than the coronavirus. It affected 29 countries and resulted in more than 8,000 cases and 700 deaths. Transmission was primarily from person to person. Implementation of infection control practices—social distancing, quarantine, surveillance, masks, etc—brought the global outbreak to an end.

Both SARS-CoV and the virus that causes Covid-19 were transmitted via droplets from coughs/sneezes. SARS had a mortality rate of around 10 per cent, higher than Covid-19’s current mortality rate. The notable difference was that even during the height of the SARS epidemic, the risk of transmission to travellers was low.  This was, however, an exceptional case since it mysteriously disappeared in 2004 before a vaccine could be developed.

The first pandemic to be eliminated by a vaccine was Smallpox. It was described as “the most dreadful scourge of the human species”. Today it’s a medical success story, but before it was eradicated, the smallpox virus raged for 3,000 years decimating communities across the world. In the late 18th-century, a British doctor named Edward Jenner discovered that milkmaids infected with a milder virus called cowpox seemed immune to smallpox. Jenner famously inoculated his gardener’s 9-year-old son with cowpox and then exposed him to the smallpox virus with no ill effect. The vaccination he formulated helped stop the pandemic but it was not till 1980 that the World Health Organization announced that smallpox had been eradicated. While it raged, however, smallpox was as deadly as any virus faced by mankind.

In modern times, the deadliest virus has been HIV. It has claimed the lives of more than 32 million people and currently, around 38 million people are living with HIV. Although HIV is also caused by a virus, there are significant differences between the two current pandemics; the most obvious being their means of transmission. Unlike SARS-CoV-2, which is the virus that causes Covid-19, HIV is transmitted via the bodily fluids of someone infected with the virus, most commonly during unprotected sex or using the same drug injection equipment. There is no vaccine to treat HIV-AIDS but there are anti-retroviral medications which allow people to live long and healthy lives.

The deadliest pandemic ever recorded was the Black Death which hit Europe in 1347 and claimed 200 million lives in just four years. The Black Death, also called the Great Plague of London, was the last and one of the worst of centuries-long outbreaks, killing 100,000 Londoners in just seven months. The plague resurfaced every 20 years from 1348 to 1665—40 outbreaks in 300 years. It eventually waned after all public entertainment was banned and victims were forcibly shut into their homes with red crosses painted on their doors. Londoners began to self-quarantine, stopped travelling as freely, and, when in public, covered their mouths and noses with handkerchiefs soaked in perfumes. This is believed to have reduced the risk of infection and transmission. Today, antibiotics are an effective antidote to a return of the plague.

The one pandemic that every scientist and health expert quotes these days is the 1918 Spanish Flu. It swept across the world in the wake of World War I, transmitted by returning soldiers who infected half a billion people around the world, (one-third of the world’s population) leaving 100 million people dead between 1918 and 1919. Why it is quoted so often these days is because of the restrictions imposed then is so similar to the world we live in today. In the US, officials imposed quarantines, ordered citizens to wear masks and shut down public places, including schools, churches, libraries and theaters. People were advised to avoid shaking hands and to stay indoors and laws were passed banning spitting. By the summer of 1919, the flu pandemic came to an end, as those that were infected either died or developed immunity. Since 1918, there have been several other influenza pandemics, although none as deadly.

In the spring of 2009, a novel influenza A (H1N1) virus emerged. It was detected first in the United States and spread quickly across the world. This new virus contained a unique combination of influenza genes not previously identified in animals or people. On August 10, 2010, WHO declared an end to the H1N1 influenza pandemic. However, the H1N1 virus continues to circulate as a seasonal flu, causing illness, hospitalisation, and deaths worldwide every year.

Among the world’s deadliest diseases, cholera ranks behind the plague and smallpox. In the 19th century, it killed tens of thousands in Britain. The prevailing scientific theory of the day said that the disease was spread by foul air known as a “miasma”. A British doctor named John Snow suspected that the mysterious disease, which killed its victims within days of the first symptoms, lay in London’s drinking water. He found a cluster of 500 fatal infections surrounding the Broad Street pump, a popular well for drinking water. Snow convinced local officials to remove the pump handle on the Broad Street drinking well, rendering it unusable, and like magic the infections dried up. Snow’s work didn’t cure cholera overnight, but it eventually led to a global effort to improve urban sanitation and protect drinking water from contamination. Cholera has largely been eradicated in developed countries but is still a persistent killer in countries lacking adequate sewage treatment and access to clean drinking water.

If any of the pandemics and killer diseases listed above offer any clues as to how the current Covid-19 will end, it lies in the measures taken to contain their spread—hygiene, quarantine, social distancing, face coverings, clean drinking water, isolation of those infected, surveillance, and closure of places which involve public gatherings. Only one of the pandemics, smallpox, ended with a vaccine. It may be of little consolation in the present circumstances, but it may help, psychologically, to remember that we are not the only humans to have experienced such unprecedented challenges— and we will not be the last. The upside, however feeble, is that history tells us that pandemics do end, and that modern science and medicine offer hope that we are better armed than those who faced the earlier pandemics.

Lead picture: UNI

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