On March 5th, local time, The Lancet Infectious Diseases, a sub-issue of the leading medical journal, published online in the form of Personal View. Can we control COVID-19 with the same measures against SARS? “。
The paper notes that while there are striking similarities between SARS (Severe Acute Respiratory Syndrome) and COVID-19 (New Coronary Pneumonia), differences in viral characteristics will determine whether the same measures taken against SARS can ultimately succeed in COVID-19.
The authors believe that there are differences between COVID-19 and SARS in terms of infection cycle, infectiousness, clinical severity and community transmission. However, even if traditional public health measures do not fully control outbreaks of COVID-19, they will remain effective in reducing the peak of morbidity and global deaths.
The article notes that China has implemented the largest quarantine in history to prevent the outbreak from spreading to other parts of the world. As of 30 January 2020, a total of 113,579 close contacts had been tracked and 102,427 had been medically observed.
“This is an unprecedented effort that exceeds previous efforts to combat SARS,” they wrote. “But there is no doubt that no other country can follow China’s lead.
The authors stress that the short-term costs of control will be much lower than those that are not controlled. However, the closure of institutions and public places and restrictions on travel and trade cannot be sustained indefinitely. Countries must face the reality that, in the long run, individual case control may not be possible and that a shift from control to mitigation is needed to balance the costs and benefits of public health measures.
The authors of this article are Annelies Wilder Smith, Professor of The ological lying seine of the University of London School of Hygiene and Tropical Medicine, University of Heidelberg, Singapore, and Calvin J Chiew, National University of Singapore Health System, Dr. Vernon J Lee, School of Public Health, Suriforschool, National University of Singapore. Smith is the paper’s correspondent who went deep into the SARS front line in 2003.
Similarities and differences between the two outbreaks
In November 2002, the emergence and rapid spread of severe acute respiratory syndrome (SARS-CoV) in China caused global alarm. As of July 2003, more than 8,000 SARS cases had been detected in 26 countries worldwide. Seventeen years later, in December 2019, a new coronavirus, SARS-CoV-2, appeared in Wuhan, China, and led to the rapid spread of the 2019 coronavirus disease (COVID-19). On January 30, 2020, COVID-19 was declared a public health emergency of international concern.
The similarities between SARS-CoV and SARS-CoV-2 are striking, the authors note, and are not just named. The overall genomic similarity of SARS-CoV-2 to SARS-CoV is 86%, and both viruses are highly homologous to SARS-like coronaviruses isolated from bats, suggesting that SARS-CoV-2 also originated in bats, as is SARS-CoV. In addition, the sources of both outbreaks are believed to be linked to the sale of a variety of wildlife and livestock markets.
Even in terms of the spread of disease, there are striking similarities between the two viruses. Despite reports that both viruses can spread through feces, the main route of transmission is respiratory droplets. Angiotensin-conversion enzyme 2 (ACE2) found in the lower respiratory tract of humans has been identified as entering cell receptors for both SARS-CoV and SARS-CoV-2.
It is currently known that the median incubation period for COVID-19 and SARS is about 5 days. The median human-to-human transmission of COVID-19 was 7.5 days, with an initial estimate of 2.2 for the number of basic infections (R0), and 8.4 days for SARS and 2.2-3.6 for R0. The risk factors for both serious disease outcomes are geriatric and comorbidities.
In addition, patient progression has a similar pattern, i.e. about 8-20 days after the first symptom appears to develop acute respiratory distress syndrome, while pulmonary abnormalities on chest CT show the most severe about 10 days after the first symptom.
However, the authors note that the similarities so far, the trajectory of the epidemic looks different.
A total of 8,098 cases were reported by SARS in 2003, of which 774 were fatal, and were eventually brought under control within eight months of July 2003. Although 26 countries have reported cases, the vast majority of cases are concentrated in China, Singapore and Toronto, Canada.
SARS is eventually brought under control by monitoring symptoms, rapidly isolating patients, strictly controlling all contacts and implementing primary quarantine in some areas. In other words, BY BLOCKING ALL HUMAN-TO-HUMAN TRANSMISSION, SARS IS EFFECTIVELY CLEARED.
By contrast, more than 82,000 confirmed cases and more than 2,800 deaths, most of them in China, had been reported in the two months since the start of the COVID-19 outbreak. With the exception of China, more than 3,600 cases have been reported in 46 countries.
The authors question: Traditional public health measures are widely used to eliminate SARS, but can COVID-19 be controlled by these same measures? They argue that it is important to analyse what was done at the time and what lessons were learned for COVID-19.
Extensive public health measures implemented during SARS
The authors note that in the absence of vaccines and treatment, the only public health tools for controlling infectious diseases are quarantine, quarantine, social alienation and community closures.
Isolation is to separate the patient from the uninfected, usually in the hospital, but also at home for mildly infected patients. The authors note that for isolation to be successful, case detection should be carried out early, i.e. before the virus is excreted or at least before the peak of the virus is released.
For SARS, the viral load peaks a few days after the onset of the disease, allowing it to be isolated early before transmission. If infected patients are isolated within 4 days of the onset of symptoms, the number of secondary cases from infected patients can be significantly reduced. For SARS patients, focus on fever or respiratory symptoms, as well as epidemiological links (contact or travel history).
They cited the low secondary home transmission rate (6.2 per cent) in Singapore during SARS, which indicates the need for rapid testing and isolation of patients. Similarly, in Toronto, Canada, the secondary home transmission rate is 10 per cent. It is worth noting that the rate of secondary transmission is linearly correlated with the amount of time spent at home after the symptoms of the indicated case (index patient) appear.
In addition, health-related transmission accounts for more than 90 per cent of all cases in Singapore. Once comprehensive measures are taken, almost all patients are quickly isolated before secondary transmission occurs. They noted that the SARS outbreak in Singapore was transmitted by five super-transmission events, three of which were caused by patients initially showing no typical SARS clinical manifestations.
Quarantine work includes restrictions on the movement of close contacts of infected patients during the incubation period and medical observation during quarantine. A successful quarantine is premised on the rapid and comprehensive tracking of each contact with each confirmed patient. Segregation can be done at home or at designated locations such as hotels, both of which have been used during the SARS epidemic.
The principle is that if a quarantined person develops a disease, it will ensure that he does not spread the disease through any close contact, effectively reducing the R0 of the outbreak to less than 1.
The authors cite strong examples of this during SARS, such as the Toronto Public Health Survey of 2,132 suspected SARS cases and the determination of 23,103 contacts to be quarantined, close contacts to be legally enforced quarantine;
Once it is not possible to identify all infected people and their contacts, the next step may be to take control measures across the community. Community-wide control is an intervention that applies to an entire community, city, or area, designed to reduce personal interaction. These interventions include encouraging individuals to take responsibility for disease identification, increasing social distances between community members, including the elimination of public gatherings and, finally, community segregation. The implementation of control measures within the community is much more complex than quarantine or quarantine due to the large number of people involved.
The authors note that China is the best example of this mass isolation. In April 2003, China took full control of all activities in the fight against SARS through the development of clear, reasonable and widely implemented guidelines and control measures at the national level. Tough controls include school closures, public places closed, and the cancellation of May Day holidays.
The immediate effect is that R0 drops dramatically and continues to be maintained.
Singapore has become the so-called “thermometer country”: schools impose temperature monitoring and temperature screening at entrances to public places. Hundreds of fever clinics have been opened and people are encouraged to check for fever multiple times a day, and case detection has been further improved.
Overall, the authors note, the more worried people, the more aware of SARS, and those with higher risk perception, the more likely they are to take comprehensive precautions to deal with infection. The public’s awareness of SARS is very high and they are very willing to accept quarantine when needed (90 per cent of respondents said they would like to do so in a psychological behavioural study conducted in Singapore and Hong Kong). All countries affected by SARS also have a strong political will to implement all public health measures in a short period of time in a top-down manner.
Hospital-based measures include isolation rooms equipped with isolation care technology, strict enforcement of personal protection by health care personnel, and restrictions on the activities of visitors and health care workers. At that time, the negative pressure chamber was basically not used, or only when it was available. Infection control prevention measures have been strengthened in all hospitals, including separate shunt facilities for patients with fever or respiratory symptoms.
In Toronto and Singapore, health care providers are required to use gloves, protective clothing, eye masks and N95 masks when receiving treatment, regardless of whether the contact is a SARS patient or not. In order to reduce in-hospital transmission, hospitals are prohibited from visiting SARS patients, except out of the principle of compassion. Health care workers or visitors who have been exposed to SARS transmission facilities are not allowed to enter non-SARS areas. In Singapore, all health care workers are required to have a temperature test twice a day. Health care providers with fever symptoms must report to a designated health care facility and be quarantined until the possibility of SARS is ruled out.
It is worth noting that in order to accommodate a large number of SARS patients(both possible and suspected), Beijing quickly built a 1,000-bed “Little Tangshan Hospital” within a week, which admitted one-in-seven SARS patients in two months.
What’s the difference between 2020 and 2003?
Seventeen years later, we can learn the lessons of SARS, the authors write.
In fact, COVID-19 is much faster from the first case of detection to virus sequencing and diagnostic development than during SARS, and diagnostic testing is available worldwide within two weeks of reporting cases in China. In addition, the Global Outbreak Alert and Response Network (GOARN), the Alliance for Innovation in Epidemiological Prevention (CEPI), and the Global Alliance for research and development of infectious disease sinare, these organizations can accelerate outbreak response and rapidly launch technology platforms to develop vaccines and therapies.
China now has higher standards of care, better-educated health care workers and more technical and scientific expertise than it did in 2003, the article said. China’s current response is more transparent and decisive, and action has begun early in the current outbreak, much earlier than when SARS was in 2003.
So why, by January 30, 2020, the number of COVID-19 cases has exceeded SARS? The authors list several possible explanations.
First, the situation is different. Under many factors, it is challenging to control the center of COVID-19. Wuhan is the largest city in Central China (11 million people), the main transportation hub and industrial and commercial center in central China, with the largest railway station, the largest airport and the largest deep-water port in Central China.
China’s outbound tourism has more than doubled in the past decade, and urban population density may even triple. In a big city like Wuhan, the proximity of people to living, commuting and working environments amplifies the spread of people.
The size of the population is the biggest challenge. Hospitals are initially overwhelmed by too many patients, many of which are not admitted because of a shortage of beds, exacerbating community spread. To make matters worse, in the days leading up to Wuhan’s “closed city”, more than 5 million people, many of them possibly carriers of the virus, were out of the city because of the proximity of the Spring Festival, which is why COVID-19 spread to other provinces in China. At the same time, Wuhan and the international airport are highly interconnected, further promoting the rapid spread of COVID-19 in Singapore, Japan, Thailand and other countries and regions.
The second explanation is that the infection period is different. Isolation is effective for SARS because the peak of virus discharge can be easily identified when the patient already has severe respiratory symptoms. In contrast, preliminary evidence suggests that COVID-19 has begun to spread at an early stage. This means that COVID-19 patients have been isolated too late in the event of a more severe illness. The effectiveness of isolating and tracking contacts depends on the proportion of transmission that occurs before symptoms occur. Pre-symptom spread also discounts the effects of temperature screening.
A third explanation is that COVID-19 may be more capable of transmitting than SARS. R0 is a central concept in infectious disease epidemiology, representing the number of continued cases caused by an infection caused by an infection without protection. In an article published february 13 in Journal of Travel Medicine, Smith and his co-authors noted that the average R0 for COVID-19 is 3.28 and the median R0 is 2.79, higher than SARS.
Of course, the authors argue that more accurate R0 can only be determined if the outbreak is stable.
There is no doubt that the rapid spread of COVID19, from the first case in early December 2019 to 80,000 cases by the end of February 2020, is clearly faster than SARS between March 2002 and March 2003, during which time SARS has no form of control.
Another example is that, as of 28 February 2020, despite public health measures, more than 700 of the approximately 3,700 passengers and crew on board the Japanese cruise ship Diamond Princess had been infected, a high infection rate that indicates a high level of infectiousness.
The fourth explanation is that the clinical scope is different. The authors note that The initial definition of cases in China was concentrated in pneumonia, and according to this narrow case definition, the reported initial fatality rate (CFR) was about 10%.
However, as the outbreak developed, it became clear that cases of mild illness were common in patients with COVID19. But even with a more sensitive surveillance system, patients with mild symptoms are left out, and these patients may spread the disease quietly, just like the flu.
It is worth noting that even if the COVID-19 fatality rate (possibly 2%) ends up well below the SARS fatality rate (10%), it is still not reassuring. Because highly contagious leads to more cases, the final death toll will be higher than SARS.
The fifth explanation is that community communication is more pronounced. SARS is mainly spread in hospitals, but for COVID-19, widespread community transmission is already evident.
As of 28 February 2020, more than 82,000 cases had been reported. Some models suggest that hundreds of thousands of infections may already exist in China. As a result, there will be more unknown contacts in the community than known contacts, which means that many of the contacts who subsequently develop into infected people are not isolated and subject to appropriate medical observation.
As a result, China has decided to implement one of the harshest of all traditional public health measures: community segregation, reduced social distances, the use of masks, and the closure of public transport in Wuhan, including buses, trains, ferries and airports.
The authors note that China has implemented the largest quarantine in history to prevent the outbreak from spreading to other parts of the world. As of 30 January 2020, a total of 113,579 close contacts had been tracked and 102,427 had been medically observed.
“This is an unprecedented effort that exceeds previous efforts to combat SARS,” they wrote. “
Will the same measures succeed? In the long run, a shift from control to mitigation may be required
The authors note that the cost behind these efforts is travel and trade, which have taken its toll on China’s economy and other sectors. These sacrifices are made because the memory of SARS has raised hopes that it will be feasible to contain the outbreak.
But will these strict measures really be as successful as they were in the SARS era? The authors argue that this depends on the extent to which subclinical cases (asymptomatic or mild) spread, including the peak time of the virus during the spread of the disease, as well as the role of pollutants and the spread of other environmental pollution.
The answers to these questions will determine success. But the authors also argue that politics and the medical profession need to continue to take control over existing tools before they know the answers. “China’s political will should be commended. But there is no doubt that no other country can follow China’s lead. “
What is known is that if some countries have the political will to detect cases quickly, isolate patients quickly, track contacts and immediately isolate all contacts, then even the export of cases to those countries will not necessarily lead to a rapid outbreak of large-scale outbreaks.
Control of COVID-19 should be the focus at present. The authors stress that the short-term costs of control will be much lower than those that are not controlled. However, the closure of institutions and public places and restrictions on travel and trade cannot be sustained indefinitely. Countries must face the reality that, in the long run, individual case control may not be possible and that a shift from control to mitigation is needed to balance the costs and benefits of public health measures.
The authors concluded that even though our public health measures do not fully control the spread of COVID19 because of the virus’s own characteristics, they will effectively delay widespread community transmission, thereby reducing peak incidence and its impact on public services.
In addition, by expanding health systems and increasing response decisions, outbreaks can be minimized or curbed, global deaths can be reduced and, of course, global transmission slowed before effective vaccines are available.