Share on Pinterest The 1918 flu pandemic led to hundreds of thousands of deaths in the U.S. Getty Images SARS, the 1918 flu pandemic, and Ebola have all helped public health officials prepare for major outbreaks.

Each major outbreak is different though, and experts have a hard time predicting how they will end.

The fallout of each disease largely depends on other circumstances — when we catch it, how contagious and fatal it is, how hygienic people are, and how quickly a vaccine or cure becomes available. All data and statistics are based on publicly available data at the time of publication. Some information may be out of date. Visit our coronavirus hub and follow our live updates page for the most recent information on the COVID-19 outbreak. With new cases of the new coronavirus disease, COVID-19, growing day by day, it’s natural to compare the new disease to other outbreaks in recent history. There was the 1918 influenza, for example, that infected nearly a third of the world’s population before it fizzled out. Then came other threatening viruses that appeared out of nowhere: severe acute respiratory syndrome (SARS), the H1N1 influenza in 2009, and Ebola. Eventually, we got a handle on all of them. But the fallout of each disease largely depends on other circumstances — when we catch it, how contagious and fatal it is, how hygienic people are, and how quickly a vaccine or cure becomes available. The death rate isn’t the only determining factor regarding how devastating and deadly a pandemic will be, according to Dr. Christine Kreuder Johnson, a UC Davis professor of epidemiology and ecosystem health and researcher on USAID’s Emerging Pandemic Threats PREDICT project. Here, we’ll take a look at how COVID-19 stacks up to other major outbreaks so far:

1918 influenza The 1918 Spanish flu epidemic was the deadliest flu season we know of, infecting about one-third of the world’s population. “The 1918 pandemic strain of influenza was new and novel for most people under the age of 40 or 50, but that’s where the death rate really was high — that’s different than the usual flu,” said Dr. Mark Schleiss, a pediatric infectious disease specialist with the University of Minnesota. Back then, scientists didn’t know viruses caused disease, and we didn’t yet have a vaccine or antivirals to help prevent or treat influenza, nor did we have antibiotics to treat secondary bacterial infections. Life was also very different back then — for one, we were in the middle of a war and soldiers carried the virus with them all over the world. People were also living in very crowded conditions and had extremely poor hygiene — this helped the disease build and build, according to Johnson. Key symptoms: fever, nausea, aches, diarrhea

fever, nausea, aches, diarrhea First detection: March 1918

March 1918 Global cases : 500 million

: 500 million Global deaths: over 50 million (675,000 in the United States); the death rate was around 2 percent

over 50 million (675,000 in the United States); the death rate was around 2 percent Transmission: spread through respiratory droplets

spread through respiratory droplets Most affected groups: otherwise healthy adults ages 20 to 40

otherwise healthy adults ages 20 to 40 Treatments available: none; antibiotics or antivirals did not yet exist

none; antibiotics or antivirals did not yet exist Vaccines available: none

none End of pandemic: summer 1919; mostly due to deaths and higher immunity levels

Seasonal flu The flu strikes every year, but no two seasons are exactly the same. Because strains mutate each year, it can be hard to predict what will hit. Unlike COVID-19, we have effective vaccines and antiviral medications that can help prevent and reduce the severity of the flu. Additionally, many people have residual immunity to the flu from years past, as our bodies have seen the flu before. We don’t have any immunity to COVID-19, and it appears to be more contagious and fatal than the flu so far, but this could very well change as we learn more. Key symptoms: fever, cough, sore throat, fatigue

fever, cough, sore throat, fatigue Global cases annually: 9 percent of the population, or about 1 billion infections (up to 5 million of which are severe)

of the population, or about 1 billion infections (up to 5 million of which are severe) Global deaths annually: between 291,000 to 646,000 ; death rate around 0.1 percent

between ; death rate around 0.1 percent Transmission: spreads through respiratory droplets; each diagnosed person passes it to 1.3 persons

spreads through respiratory droplets; each diagnosed person passes it to 1.3 persons Most affected groups: older adults and people with compromised immune systems

older adults and people with compromised immune systems Treatment available: antiviral medications (Tamiflu, Relenza, Rapivab, Xofluza) to reduce duration and severity of flu

antiviral medications (Tamiflu, Relenza, Rapivab, Xofluza) to reduce duration and severity of flu Vaccines available: there are many vaccine options available that provide immunity against multiple strains of influenza

2002–2004 severe acute respiratory syndrome (SARS) SARS is another type of coronavirus that came out of China and spread quickly through respiratory droplets. Though the SARS death rate was higher than COVID-19, COVID-19 has already claimed more lives. According to Johnson, contact tracing — or monitoring people in close contact with those who contracted it — was really effective with SARS, largely because symptoms were severe and therefore easier to identify and contain. In addition, Schleiss said the SARS virus didn’t have the “fitness to persist in the human population,” which eventually led to its demise. Schleiss added this doesn’t seem to be the case with COVID-19, which seems to be able to spread and thrive in the human body. Overall, though SARS’ death rate was higher, COVID-19 has led to “more fatalities, more economic repercussions, more social repercussions than we [had] with SARS,” Johnson said. Key symptoms: fever, respiratory symptoms, cough, malaise

fever, respiratory symptoms, cough, malaise First detection: November 2002 in Guangdong province of China

November 2002 in Guangdong province of China Global cases: 8,098 cases across 29 countries; 8 U.S. cases

across 29 countries; 8 U.S. cases Global deaths: 774; 15 percent mortality rate; no U.S. deaths

774; 15 percent mortality rate; Transmission: spread through respiratory droplets and contaminated surfaces

spread through respiratory droplets and contaminated surfaces Most affected groups: patients 60 and older had a 55 percent higher death rate

patients 60 and older had a 55 percent higher death rate Treatment available: no treatment or cure, but antiviral medications and steroids worked for some people

no treatment or cure, but antiviral medications and steroids worked for some people Vaccine available: a vaccine was ready around the time the pandemic was already ending

a vaccine was ready around the time the pandemic was already ending End of pandemic: July 2003

2009 (H1N1) flu pandemic Back in 2009, a new type of flu — an H1N1 strain — popped up and people panicked because we didn’t have a vaccine and the novel strain was spreading fast. Like COVID-19, there was no immunity at the start of the outbreak. We did have antivirals to facilitate recovery, and by the end of 2009, we had a vaccine which — combined with higher levels of immunity — would provide protection in future flu seasons. Still, it claimed over 12,000 lives in the United States. Key symptoms: fever, chills, cough, body aches

fever, chills, cough, body aches First detection: January 2009 in Mexico; April 2009 in United States

January 2009 in Mexico; in United States Global cases: about 24 percent of global population; 60.8 million U.S. cases

about 24 percent of global population; 60.8 million U.S. cases Global deaths: over 284,000; 12,469 in the United States; death rate was .02 percent

over 284,000; 12,469 in the United States; death rate was .02 percent Most affected groups: children had the highest rates; 47 percent of children between 5 and 19 developed symptoms compared to 11 percent of people ages 65 and up

children had the highest rates; of children between 5 and 19 developed symptoms compared to 11 percent of people ages 65 and up Treatment available: antivirals (oseltamivir and zanamivir); most people recovered without complications

(oseltamivir and zanamivir); most people recovered without complications Vaccine available: H1N1 vaccine research started April 2009 and a vaccine became available December 2009

H1N1 vaccine research started April 2009 and a vaccine became available December 2009 End of pandemic: August 2010

2014–2016 Ebola Ebola was extremely deadly, killing up to 50 percent of those who got sick. But because it predominantly spread through bodily fluids like sweat and blood during the last stages of the disease, it wasn’t as contagious as COVID-19. Plus, because symptoms were so severe, health officials were able to quickly identify those who’d been in contact with people who had it and isolate them. “You don’t have relatively healthy people with the [Ebola] virus walking around shedding the virus — going on the bus, going shopping, going to work — like we do with this,” Johnson said. Key symptoms: fever, aches and pains, weakness, diarrhea, vomiting

fever, aches and pains, weakness, diarrhea, vomiting First detection: first patient identified December 2013 in Guinea; first outbreak March 2014

first patient identified December 2013 in Guinea; first outbreak Global cases: 28,652 cases across 10 countries

across 10 countries Global deaths: 11,325 deaths; death rate was about 50 percent

11,325 deaths; death rate was about Transmission: spread through bodily fluids (blood, sweat, feces) and close contact; most contagious toward end of disease

spread through bodily fluids (blood, sweat, feces) and close contact; most contagious toward end of disease Most affected groups: 20 percent of all cases occurred in children

of all cases occurred in children Treatment available: none; supportive care was provided, including IV fluids and oral rehydration

none; supportive care was provided, including IV fluids and oral rehydration Vaccines available: none

none End of outbreak: March 2016

Novel coronavirus (COVID-19) Early evidence shows COVID-19 may be more contagious than the flu. And some early reports say COVID-19 may have a higher death rate than the seasonal flu. But we may soon find out it’s less deadly than initial reports since so many people with COVID-19 have mild symptoms or are asymptomatic and therefore don’t see a doctor and are largely unaccounted for. “The death rate really is something we just have to take with a grain of salt until we have enough information,” Johnson said. This is a rapidly evolving situation, and numbers and estimates are likely to change as we learn more. Key symptoms: cough, fever, shortness of breath; 80 percent of cases are mild

cough, fever, shortness of breath; 80 percent of cases are mild First detection: December 2019 in Wuhan, China

December 2019 in Wuhan, China Global cases to date: Over 127,000 cases

Over 127,000 cases Global deaths to date: Over 4,700; the global death rate is estimated at 3.4 percent , but certain areas are seeing a death rate of just 0.4 percent

Over 4,700; the global death rate is estimated at , but certain areas are seeing a death rate of just 0.4 percent Transmission: spreads through respiratory droplets along with feces and other bodily secretions; each person passes it to 2.2 others which will likely fall as containment and quarantine efforts increase

spreads through respiratory droplets along with feces and other bodily secretions; each person passes it to 2.2 others which will likely fall as containment and quarantine efforts increase Most affected groups: adults over 65 with underlying health conditions; children seem to be spared and are experiencing milder symptoms (in China, children account for just 2.4 percent of cases)

adults over 65 with underlying health conditions; children seem to be spared and are experiencing milder symptoms (in China, children account for just 2.4 percent of cases) Treatments available: none; supportive care is provided, pain relievers and fever reducers can alleviate symptoms, and antibiotics can help treat secondary bacterial pneumonia and antivirals used with other viruses are being administered to help with recovery

none; supportive care is provided, pain relievers and fever reducers can alleviate symptoms, and antibiotics can help treat secondary bacterial pneumonia and antivirals used with other viruses are being administered to help with recovery Vaccines available: none yet; a vaccine will likely be ready in about one year

So, when will things calm down with COVID-19? According to Schleiss, it’s going to take herd immunity — which basically blocks out the virus when a large chunk of the population is immune from already being sick — along with an effective vaccine. “We really, really need a vaccine,” he said, adding that because the Food and Drug Administration will need to prove a vaccine is safe, it could take a year or two — best case scenario. We also have a lot more we need to learn: the prevalence of the infection along with how you contract the virus and all the different roads of transmission. Until then, we’re going to need to practice social distancing to help minimize the number of people who contract it, says Johnson. We’ll need to work together to limit exposure to one another — especially with older adults and people with underlying illness who have the greatest risk of developing severe symptoms. We don’t need to panic. Remember: The vast majority of COVID-19 cases are mild. But we do need to take action to contain the spread and protect those who are most vulnerable.