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Remembering SARS: A Deadly Puzzle and the Efforts to Solve It

In the 2003 global disease outbreak, what became known as SARS-CoV started as a mystery illness—without name, origin, or cure. Public health scientists across the globe scrambled to understand and contain this health threat.

CDC began working with the World Health Organization (WHO) in late February to investigate and confirm outbreaks of an unusual pneumonia in Southeast Asia. As WHO led a global effort to understand the illness and how to prevent its spread, questions outnumbered answers. At the time, all that was known about the new disease was that people quickly become severely ill and that it could be fatal.

By the time WHO issued a global alert on March 12, cautioning that the severe respiratory illness may spread to hospital staff, CDC had confirmed this was not “bird flu,” the influenza A (H5N1) that had been reported recently in Hong Kong. The mystery illness was given a name: Severe Acute Respiratory Syndrome (SARS), although scientists still did not know which microbe was causing SARS.

On March 14, the response to this health threat became more urgent for CDC when several SARS cases were reported in Canada. That same day, CDC activated its Emergency Operations Center (EOC).

A CDC-Wide Response

For decades, when invited by the WHO or Ministries of Health, CDC has lent expertise to global disease outbreak responses. Typically, CDC’s infectious disease centers manage those responses. However, when the response effort may need more staff and supplies than usual or when the response might go on for an extended time, the CDC Director can activate the EOC. Activating the EOC means the incident commander can assemble expert staff and volunteers from across the entire agency to help.

During the 133 days of CDC’s emergency response phase of the SARS outbreak, more than 850 people from across the agency were deployed to the EOC. Within hours of activating the CDC response, 112 staff were deployed to response teams, CDC laboratories, and affected countries. Within 3 days, 200 staff were working 24/7 on the response.

Staff assignments were far reaching in scope:

  • Develop a case definition so medical staff could determine who may or may not have SARS
  • Offer case-by-case consultation to public and private healthcare providers
  • Provide guidance on managing the care of patients
  • Provide guidance on how to protect health workers on the job
  • Determine in the lab what was causing SARS
  • Once the microbe was identified, create diagnostic tests
  • Provide guidance on isolation and quarantine to prevent spreading the disease
  • Track and analyze cases to define risk and stop disease spread
  • Monitor travelers’ health at points of entry to the United States
  • Communicate health messages to the public, especially travelers
  • Report U.S. cases to WHO

While the urgent tasks of disease outbreak response was ongoing, CDC scientists also considered the possibility that this outbreak could became a pandemic? On March 28, CDC began developing pandemic response plans (Team “P”) in case the SARS epidemic became uncontrollable. Team P was supported by the Mathematical Modeling team who calculated the expansion of the outbreak.

Most CDC staff deployed for the SARS response worked on teams at CDC’s headquarters in Atlanta. However, 235 staff went into the field; 67 were deployed to 10 international locations. Domestically, CDC sent 165 staff to 19 points of entry, including quarantine stations already staffed by CDC. Deployments ranged in length from 1 to 133 days; average 45.

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Identifying the Cause

On March 24, CDC reported that its lab scientists, along with scientists from collaborating international labs, believed SARS may be caused by a new virus from the coronavirus family.

By April 14, CDC had identified the complete genetic sequence of the new virus—adding a critically important 15 additional nucleotides to the beginning of the sequence determined by a Canadian laboratory two days earlier. These results came just 12 days after a team of 10 scientists began working around the clock to identify the etiologic agent from a throat culture from a patient with SARS.

With the complete gene sequence known, scientists could then start to look for drug treatments, diagnostic tests and possible vaccines to prevent or treat the new coronavirus. Lab tests to rapidly identify infected people would be an important step in reducing spread of SARS.

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Can We Stop It?

While still not fully knowing how SARS spread, CDC focused on detecting cases as early as possible and applying infection-control measures in health-care settings and the community to limit SARS in the United States.

Based on outbreaks in healthcare settings outside the United States, it appeared that some healthcare workers did not know how best to use protective equipment to avoid contaminating themselves, especially when removing gloves and masks.

To protect healthcare workers, CDC advised using strict infection control actions to keep SARS from spreading from ill patients to those caring for them. Specifically, the use of N-95 respirators and surgical masks in hospitals could work. The masks could also help to stop the potential spread in communities.

However, CDC recommended training to correct the way workers used and removed protective equipment and stressed the importance of hand hygiene. The N-95 respirator is typically worn by healthcare workers to prevent exposure to airborne disease like tuberculosis. However, if the mask doesn’t fit correctly, it doesn’t do a very good job of keeping them from breathing in very small germs that may hang in the air after a sick person coughs.

Healthcare workers or visitors who had direct contact with patients were advised to wear N-95 respirators and CDC recommended that patients should be cared for in special air isolation rooms.

By March, CDC scientist knew that the research, thus far, indicated that fairly prolonged contact, face-to-face, was typically how SARS spread from person to person. However, CDC’s disease detectives had begun to collect information that suggested it spread from much briefer contact between people. An entire investigative team from CDC was exploring cases of spread among people in hotels where guests came in contact with sick people only briefly. During these instances as well, CDC recommended strict infection control measures including hand washing, gloves, avoiding sharing household items, and limiting interaction between ill patients and others.

CDC also advised on quarantine and isolation methods to help prevent community spread.

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Solving the Mystery of “Super Spreaders”

While we may never know with certainty where the SARS virus originated, it likely moved from animals to humans. Lab research confirmed that SARS can infect a number of animals, including palm civets that live in China where the 2003 outbreak originated. A civet is a meat-eating mammal that has a cat-like appearance, but the animal is not a cat.S ARS-CoV was also found in the blood of animal handlers.

In the 2003 outbreak, in some instances outside the United States, a single SARS patient infected large numbers of people. At the same time, other patients did not infect people who came in contact with them.

Researchers found that the virus was typically spread from person to person by large droplets (less efficient spread because it would be too big to linger in the air); however, at other times, clusters of illness suggested aerosol spread (where the virus can linger in the air longer after an ill person coughs) causing more spread of infections from a single sick person.

CDC investigated the so-called “super spreaders.” They wanted to know if there were differences in when and for how long people ill with SARS might shed the virus, making them contagious to others. In the past, super spreaders had been documented during other disease outbreaks such as rubella, tuberculosis and Ebola. A common feature of super spreaders was that hospitals served as a source for the disease to widely infect others.

By May 9, CDC had investigated five people with probable SARS they categorized as super spreaders. These patients had infected 10 or more healthcare workers, family members, and social contacts while hospitalized.

In one instance, a 22 year-old visited Hong Kong for a shopping trip and, later while staying at a hotel, developed fever and cough which led to hospitalization. The patient was directly linked to probable SARS infections in 21 people during her hospital stay; nine healthcare workers and 12 family members or visitors.

In another case, a 60-year- old was hospitalized with kidney disease and released. He was readmitted days later for gastritis. A total of 62 people with probable SARS were linked to his case; 25 healthcare workers, 20 other patients, and 17 family and social contacts.

During the investigation, CDC determined that these “super spreaders” or large clusters of cases could not be predicted based only on whether people took precautions to prevent infection. They documented that in some instances where precautions were not used, such as using gloves, face masks and hand washing, ill patients still did not infect others.

CDC also found that super spreading events were more likely when the person was severely ill, when the patient was in contact with many more people (greater potential for spread) and if the patient was older aged.

These patients became hidden reservoirs of infection on the wards or in the community. Investigators determined that people with other health problems made it more difficult for their illness with SARS to be detected. CDC recommended, during the SARS outbreak, that patients with other health conditions who also had fever should be isolated.

These clusters of illness were puzzling. They were also a reminder how important early detection and access to information on outbreaks of unexplained illness can be. “When you first see a cluster, people need to recognize that these clusters can have global implications, and this is a dramatic example of that,” Dr. Jim Hughes, who led the CDC outbreak response, said during a March 18, 2003, teleconference.

Credible information has to be monitored in a real-time fashion to detect new diseases that may emerge from nature or from deliberate acts. Information about patterns of illness in a population may come from pharmacies, hospitals, laboratories, or Internet searches.

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Determining a Case Definition

In the United States, CDC defined a case of SARS in three ways: patient symptoms, possible exposure to the illness, and, later, by lab results.

During the outbreak, state and local health departments reported 1,460 unexplained respiratory illnesses to CDC. Of those, 398 appeared to be SARS based on patient symptoms and possible exposure through travel. Only 72 of the 398 had chest X-rays that looked like pneumonia moving them from possible cases to probable cases of SARS. Only eight of the 72 probable cases were confirmed by lab results to be SARS. No one died from SARS in the United States.

An outbreak investigation needs a good case definition to help public health officials know who is ill from the disease and who is not. Describing the outbreak’s intensity requires identifying accurately who is ill.

The early case definition for SARS included a cluster of symptoms like fever and respiratory illness from an unknown cause. In addition, the ill person also had to have traveled to affected areas within 10 days of symptoms beginning or been in close contact with someone who traveled in affected areas.

CDC sent its case definition to state and local health departments. At the beginning of the outbreak, CDC asked state and local health departments to report all respiratory illnesses that they thought should be evaluated for SARS, casting a wide net.

An Atlanta-based team at CDC collected the reports and when a patient met the case definition, the patient’s data was added to a “line list.” This data could be analyzed to determine who was at greatest risk and how the illness progressed. In 2003, reporting this information was paper-based and the information was then entered electronically and merged with laboratory data.

Intense laboratory work went on at CDC and across the CDC-supported laboratory response network.

During the outbreak, labs were testing for alternate causes for a patient’s illness. Early on labs were looking for multiple types of pneumonia, influenza viruses and other viral respiratory illnesses. The list was exhaustive but necessary to rule out other microbes that could be causing illness. As specimens flooded in, patients, hospitals, and communities waited to see if they had a case of SARS. During the early phase of the outbreak, anxiety was high among patients, healthcare workers, public health officials and the public because we did not have a rapid test to reliably diagnose SARS infection.

During this time the United States was also experiencing seasonal flu. So while more than 1,000 unexplained respiratory illnesses were reported to CDC, countless additional illnesses were investigated and ruled out for SARS by state and local health departments. This response also relied on astute healthcare providers to detect and report illnesses that might have been SARS.

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Issuing Travel Advisories and Alerts

SARS was introduced to the United States through air travel. The United States had eight lab-confirmed cases of SARS and no deaths. SARS, for the United States, was a travel-associated illness.

During the outbreak, CDC quarantine officers handed out health alert notices to passengers arriving from 11,480 flights originating from areas with SARS. CDC officials were meeting planes, cargo ships and cruise ships coming to the United States from China.

The most visited spots on CDC’s website during the outbreak where those related to travel safety. SARS was a severe illness with a short incubation period (the time from exposure to illness). CDC, in the midst of the outbreak, determined it needed to rank levels of concern about potential risk to travelers. Up to that time, CDC had never advised against travel to any region, even during the plague epidemic in India in 1994. So CDC explained its new ranking system.

  • A travel alert from CDC was a notification that an outbreak of disease is ongoing in a geographic area.
  • A travel advisory recommended against travel to an area unless essential.

Once issued, downgrading an advisory to alert required good disease detection in the area combined with no evidence of ongoing spread.

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Protecting Healthcare Workers

As the outbreak of SARS unfolded in Southeast Asia, hospital workers were becoming ill from contact with ill patients. In the United States the SARS virus did not spread within a community or a hospital. No healthcare worker became infected with SARS. In Singapore, Canada, and Vietnam the illness spread among healthcare workers but was stopped from spreading into the wider community. However, in China, Taiwan and Hong Kong the disease also spread widely in the community. In the United States, based on lab results, only one possible household transmission of SARS was reported and no healthcare workers acquired SARS from patients.

CDC offered guidance for healthcare workers and other occupations such as people in the hotel and travel industry about ways to avoid becoming ill with SARS.

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Communicating with the Media and the Public

By the early spring of 2003, the airline and tourism industries had lost billions of dollars due to public fears about SARS. Globally, some airlines and businesses declared bankruptcy as a result. The public wanted information to help protect themselves and their loved ones from an illness without a treatment. Misinformation was high and, in some cases, people believed they could avoid illness by avoiding people who looked Asian. CDC’s communication staff worked tirelessly to answer the tough questions from the public and to manage expectations about the speed of the response and reduce stigmatizing behaviors.

The communication response included:

  • 10,166 press calls triaged
  • 21 telebriefings announcing latest SARS information
  • 23 Health Alert Network messages sent to public health, clinicians and media subscribers
  • 2,079 clinicians consulted through CDC’s Clinical Information Line and 18 updates sent through the Clinician Registry with nearly 600,000 messages distributed.
  • 3 SARS satellite broadcasts with about 1.9 million participants
  • About 17 million page views on CDC SARS website, peaking the week of April 20-26

By May the SARS outbreak was waning; however, people remained fearful of the outbreak and were sometimes uncertain about how to balance avoiding the risk of infection with getting on with life. In fact, CDC issued guidance to businesses and universities who were restricting the presence of people who traveled from China.

Dr. Julie Gerberding, then CDC director, said, “It’s very important that people appreciate that this is a respiratory illness caused by a virus, probably a new virus, and is not a disease that is in any way related to being Asian. So we want to ask people’s support and help in recognizing how difficult this is for people and take the high road. This is a time when all of our communities need support and empathy, not stigma or bias or shunning that has been reported in some international press.”

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Addressing Future Challenges

It took many types of public health actions globally to contain SARS in six months. When the SARS virus reached Hong Kong in 2003, it had a fast track to all points in the world and it was finally stopped using the tools of disease detection (known as epidemiology):

  • The path of the disease had to be tracked
  • The rate of spread had to be calculated
  • The clinical case needed to be defined
  • Guidance for treatment had to be created
  • Restrictions on travel were needed, and
  • Lab scientists had to tease out the microbe’s origin

Ultimately that work was done. Without question, future mystery illnesses will emerge. The questions will be the same—what is causing the illness, where did it come from, can it be contained, who is at greater risk? The cost in lives and economic upheaval from future mystery illnesses will depend, in part, on how quickly we can detect the threat and answer the questions of life and death.

“Ten years ago a global outbreak of SARS emerged. In six months SARS killed hundreds of people and cost tens of billions of dollars,” said CDC’s current Director, Dr. Tom Frieden. “A decade after the SARS epidemic we’ve made progress but we remain at risk from global health threats.”

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Disease Detectives

The basic tools of shoe leather and spreadsheets that CDC’s disease detectives relied on to answer outbreak questions on smallpox, legionnaires, e-coli and SARS can’t be replaced; but, new tools can make our disease detectives more precise and faster in solving health mysteries. Molecular tools and bioinformatics exist today and without these tools CDC runs the risk of delays in confronting deadly health threats.

The threat to our nation’s health security doesn’t start when we first spot a new killer superbug. The looming threat to our nation’s health security starts when CDC fails to keep pace with the rapidly growing field of molecular diagnostics. Without these tools, the advantage goes to the superbugs. CDC’s current capacities in these “next generation” tools do not meet the challenges of this rapidly evolving field. Genetic sequencing of infectious pathogens could revolutionize how CDC investigates and controls outbreaks.

Genomic sequencing rapidly generates massive amounts of information on a pathogen and it is bioinformatics that helps put the puzzle together quickly, accurately, and at decreased cost. By using molecular typing, CDC could more quickly find patterns that answer the “who, what, when and how” these pathogens kill.

With enhanced molecular-based science and bioinformatics CDC could rapidly and correctly diagnose infectious diseases, more quickly control outbreaks, recreate disease transmission patterns, tackle antimicrobial resistance, and target interventions, like vaccines. “We have a unique window of opportunity,” Frieden said. “The world is committed to reducing threats to health and we have new technology that can take many important disease threats off the table, if we act now.”

The 2003 SARS outbreak starkly proved the world’s collective economic vulnerability to epidemic shocks. Fragile business alliances, trade, and travel were instantly in jeopardy as people across multiple continents waited for public health scientists to solve the mystery: what was killing patients and the health workers attempting to care for them. This uncertainty resulted in tens of billions of dollars in economic loss in less than six months.

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Global Response

In the first decade of the 21st Century, novel influenza, bioterrorist threats with anthrax, and constantly evolving microbes tested the limits of 20th century public health models. “We face a perfect storm of vulnerability,” Frieden explained. The threats of new microbes, resistant microbes outsmarting the drugs to treat them, global risks in travel and trade, and the ease of creating deadly microbes in boutique labs push the limits of acceptable risk. The global response to health threats must change.

While detecting a new disease threat, assessing the risk to individuals and populations, identifying the microbe, guiding the treatment, and containing the spread in less than 6 months is no small feat, the timeline between detecting and responding must be shortened.

Within weeks of the WHO’s first reports of what became known as SARS, people were already ill across continents. Imagine a world that could detect early and respond rapidly to an emerging threat—where local disease detection in even remote areas replaced disease detection at national borders. Global public health is shifting the focus from control at borders to disease detection and control at the sources.

There is a brief window of opportunity to contain pressing threats if the capacity is built in all countries, even the poorest countries. Every country needs at least active surveillance systems, capacities for laboratories, disease detectives, trained rapid response teams, and drugs or vaccines to control disease. The updated WHO International Health Regulations require nations to investigate, assess threats, respond and, importantly, disclose known and suspected threats without delay.

CDC continues to lead in helping standardize lab work, train disease detectives, and introduce new mobile devices to quicken decisions with data collected in a community. CDC supports WHO’s approach to adopt the same norms, rules, and processes to link data from multiple sources to help public health and healthcare workers put information to use.

For decades CDC has been a leader in containing major global health threats. “CDC will continue to work 24/7 with our international partners to detect threats quickly, respond rapidly, and prevent new threats from emerging,” Frieden said.

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While disease investigators were determining where this emerging disease had traveled and who was more likely to get sick from the disease, lab scientists wanted to find what microbe was at fault. The lab experts wanted to unlock any clues to help rapidly diagnose and then treat or cure the disease.

The clues did not come easily. For CDC, an initial challenge was simply receiving samples in good enough shape to test. Early in the outbreak, SARS was happening half way around the globe from the United States, and CDC was not receiving the samples it needed to keep pace with the outbreak.

In mid-March, CDC’s lab scientists were working around the clock on the specimens they had received—comparing any microbes they detected with reference samples kept from previous outbreaks. Nothing was matching. CDC admitted, “We are looking at bacteria. We’re looking at viruses. We’re looking at atypical bacteria. We are checking for absolutely everything.” In a March 17 teleconference, CDC reported its scientists were not suspicious that this was a common organism, or “we would have found it by now.”

CDC scientists were confident they would identify the disease, but knew it would take more than one sample to definitively name the microbe causing the illness called SARS. It would not be enough to just find it in one person. The scientists would need to find the microbe in most of the people who had been ill and, just an important, not find it in people who had not been identified as having SARS.

The challenge was the quality of the specimens. While lung tissue or blood samples were shipped to CDC from patients who had died, the key was to have samples from early in the course of the disease. CDC emphasized the need to get respiratory secretions and blood samples from people who had only recently developed symptoms. If respiratory secretions came from people after they had started to recover, it could be impossible to detect the microbe.

Nucleic acid testing was an important element to unraveling the secrets of this outbreak. Some viruses could not be grown in lab cultures or they would take a very long time to grow in numbers high enough to be detected by current lab technology. With speed a factor, CDC had to resort to the most sensitive nucleic acid technology that it had in 2003. And, sometimes, that led to false negatives from those tests.

By March 24, CDC reported its labs cultured coronavirus from two patients. In one patient, the tissue was culturing (growing) virus and the scientists could see the virus. They described it—a circular virus that looks like it has a corona or sort of crown effect, and that is basically little spikes of protein that surround the virus which gives that appearance.

Still cautious, CDC scientist, Dr. Larry Anderson admitted, “We’re finding evidence of it in actual affected tissue, including in kidney tissue from one patient.” Confidence increased when CDC’s labs found that the patient’s blood antibody test from early in his illness was negative and by the end of his illness, the antibody test had turned positive. So, in other words, the patient “seroconverted”—meaning he had a negative test and then a positive test. This change in antibodies in the blood implied the microbe caused the illness.

CDC had found the virus genetic material in lung secretions and lung tissue. In collaboration with laboratory partners in the global arena, evidence was mounting that this new coronavirus was causing SARS. “We know from sequencing pieces of the virus RNA that it is not identical to the coronaviruses we’ve seen in the past.”

On March 27, CDC’s director for infectious diseases, Dr. Jim Hughes said, “Labs in many countries now have found evidence of coronavirus infection in these patients. That’s in contrast to just a few days ago, you may recall, when metapneumovirus was clearly the leading candidate. I would say coronavirus likelihood is going up. Metapneumovirus likelihood is going down. We keep an open mind on these things. And the possibility of some co-infection, at least in some patients, has to be kept in mind.

Anderson explained, “We pursued metapneumovirus, but continued to look for other agents. A group in Hong Kong and Germany identified some particles and secretions that suggested not a paramyxovirus by size. Our electron microscope identified coronavirus-like particles in tissue culture. We then used molecular techniques to look at the genetics of this virus and confirmed that is was, in fact, a coronavirus. We then developed tools to look at additional specimens and provided the tools to other laboratories.”

Using a secure Internet site, laboratories were sharing pictures of the virus so they could understand each other’s work. The global scientific community came together to combat a global epidemic.

Hughes noted, “Ten days ago we didn’t have any antibody test to detect infection with this previously unrecognized coronavirus. As a result of a lot of hard work that’s been done here over the past 10 days, we now have two tests that look promising. They appear to perform well in suspect cases.”

To check the accuracy of the new tests, CDC looked for evidence of the coronavirus antibody in blood collected from 400 people around the United States without any suggestion of SARS, and they were all negative. The diagnostic test worked.

The scientific achievements in the first week after receiving lab specimens were “truly unprecedented.” CDC’s lab scientists developed a test to send to health departments across the nation to improve the diagnosis of SARS. A more accurate and more rapid diagnostic tool would help identify who was or was not sick form SARS so resources to contain the outbreak could be concentrated where needed.

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Health Security in Action

On March 15, 2003, following the World Health Organization’s global alert three days earlier, CDC issued its first health alert in the SARS outbreak.

CDC explained, “The emergence of two clusters of this illness on the North American continent indicates the potential for travelers who have been in the affected areas of Southeast Asia to have been exposed to this serious syndrome. We do know that it may progress rapidly and can be fatal.”

During the investigation into the SARS outbreak, CDC’s quarantine staff played an important role in the following ways:

  • Provided information to returning travelers arriving in the United States either directly or indirectly from Hong Kong, Guangdong Province, People’s Republic of China and Hanoi, Vietnam on airplanes, cargo ships or cruise ships
  • Distributed health alert notices to those travelers advising them that they may have been exposed to people who had SARS and recommending they monitor their health for at least 7 days and to contact their physicians if they become ill with a fever accompanied by a cough or difficulty breathing;
  • Boarded airplanes and ships with travelers reported to be ill to assess whether their symptoms match the case definition of SARS
  • Provided timely updates to government agencies partnering in these activities as well as to travel industry organizations;
  • Worked with CDC’s SARS investigation team and local and state health departments to assist in the investigation of suspected cases of SARS.

Dr. Marty Cetron, who was with CDC’s Division of Global Migration and Quarantine in 2003 and is now its director, explained how isolation and quarantine contributed to the outbreak response. The public and media were curious and concerned about these official and rarely used response tools.

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During a March 21 briefing about CDC’s SARS response, Cetron said: “We meet all the direct and as many of the indirect arriving flights as we're aware of, and that's an ever-increasing number. More than 50 flights a day are being met arriving from these locations where there's transmission. Now, in the event that there is a sick passenger reported either in flight in transit or at the airport on arrival, a quarantine inspector or a designee of the quarantine station will meet that flight, get on board, isolate and take off the ill passenger, and facilitate that person's going to a healthcare facility and getting that case reported.”

Since SARs, many changes and improvements have been made in CDC’s Division of Global Migration and Quarantine that will help CDC better address future threats from large outbreaks like SARS. In 2003, CDC had eight quarantine stations around the country. Partially in response to SARS but also due to greater concerns about infectious disease spread and bioterrorism, CDC expanded the number of quarantine stations to 20 (between the years 2004-2007). The quarantine stations are located at major ports of entry and land border crossings where 85% international travelers arrive. Quarantine officers are responsible for activities as various as responding to reports of illnesses, to screening cargo and inspecting animals and animal products, to monitoring the health of and collecting any medical information of new immigrants, refugees, asylees, and parolees.

In addition, CDC has taken steps to help ensure that people who are ill with a serious disease do not fly. In collaboration with the Department of Homeland Security, CDC established the national public health “Do Not Board” list in June 2007. The list is an important tool that health officials can use when they determine that someone poses a disease threat to others and is likely to travel by air. To date, the list has been used more than 250 times to prevent travelers with tuberculosis and other serious illnesses from boarding a plane.

CDC has developed better and faster ways to communicate to airline passengers who may have been exposed to a serious illness on an airplane. During SARS, CDC and its airport partners gave out 2 million printed T-HANs (Travel Health Alert Notices) with information and recommendations for people who may have been exposed to SARS while traveling.

CDC now uses electronic messaging at airports to quickly provide health messages to international travelers. During last year’s international measles outbreak, CDC posted electronic messages in airports, reaching more than 2.7 million people per month. Electronic messaging is less expensive, environmentally friendly and a faster way to reach more people than through print methods.

Following the 2009 flu pandemic, CDC established the Community Interventions for Infection Control Unit to prevent the spread of pandemic flu and other infectious diseases within communities through research and education on non-pharmaceutical interventions (such as hand washing, school closures, social distancing measures). Research in this area will help inform recommendations for future pandemics and for other illnesses like SARS.

During the outbreak, CDC quarantine officers handed out health alert notices to passengers arriving from 11,480 flights originating from areas with SARS. CDC officials were meeting planes, cargo ships and cruise ships coming to the United States from affected areas of Southeast Asia. CDC issued a travel advisory recommending against travel to Southeast Asia, unless essential. Up to that time, CDC had never advised against travel to any region, even during the plague epidemic in India in 1994.

The CDC EOC activation for SARS ended on July 25, 2003. Worldwide there were 8,096 reported cases of SARS and 774 deaths. On October 5, 2012, the National Select Agent Registry Program declared SARS coronavirus a select agent. CDC regulates the Select Agent program of biological agents and toxins that have the potential to pose a severe threat to public health and safety.

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10 Compelling Facts about SARS

  1. CDC had never advised against travel to any region, even during the plague epidemic in Indian in 1994, until the SARS outbreak.
  2. The CDC-wide activation for SARS marked the first use of its newly created Emergency Operation Center, built as a result of lessons learned from our 2001 response to the anthrax bioterrorism event, where 1,700 CDC staff responded without a dedicated EOC.
  3. Deployment statistics calculated that CDC staff contributed the equivalent of 46,714 days of work devoted to the SARS response. Another 71 people volunteered but were not deployed by the end of the response.
  4. Of the eight lab-confirmed cases of SARS in the United States, six were identified in the first month surveillance for SARS began. Five traveled to Hong Kong, two to Toronto, and one to Singapore.
  5. Among people with SARS in the United States, the majority were male (53%) with a median age of 39.
  6. In the United States, the only possible case of secondary spread was between a married couple and both had traveled internationally.
  7. SARS-CoV comes from the family of viruses that also cause the common cold in humans.
  8. In 2000, nearly 46,000 residents from China, Hong Kong, and Vietnam traveled to the United States. During the same time, about 83 million travelers arrived in China, 13 million in Hong Kong and 2 million in Vietnam.
  9. Understanding respiratory illnesses is a challenge. About 40–60 percent of people with pneumonia will never know what microbe caused the illness, even after much testing.
  10. On April 22, 2003, even after the cause of SARS was identified as a new coronavirus and the number of cases were leveling off, CDC cautioned about the epidemic, “we have no capacity to predict where it’s going or how large its ultimately going to be . . .”

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