(Photo: The Lancet)

On March 5 local time, The Lancet Infectious Diseases, a sub-issue of the top medical journal The Lancet, published an article titled "Can we contain the Covid-19 outbreak with the same measure as for SARS? "."Personal View" online in "Personal View

The article, published as "Personal View" said that while there are striking similarities between SARS (Severe Acute Respiratory Syndrome) and Covid-19 (New Coronavirus Pneumonia), differences in virus characteristics will determine whether the same measures taken against SARS will eventually Covid-19 succeeded.

The authors believe that Covid-19 differs from SARS in terms of infection cycle, infectivity, clinical severity, and community transmission.

However, even though traditional public health measures cannot fully control the outbreak of Covid-19, they will still be effective in reducing peak incidence and reducing global deaths.

The article mentions that China has implemented the largest quarantine in history to prevent the epidemic from spreading to other parts of the world. As of January 30, 2020, a total of 1,135,79 close contacts have been tracked, and 102,427 people have received medical observation.

They wrote, "This approach is an unprecedented gigantic effort that surpasses all efforts done during SARS." But there is no doubt that no other country can emulate China's current approach.

The authors emphasize that the short-term costs of control will be much lower than the long-term costs of uncontrol. However, closing institutions and public places and restricting 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 control needs to be shifted to mitigation in order to balance the costs and benefits of public health measures.

The authors of this article are Annelies Wilder Smith, Professor of the School of Hygiene and Tropical Medicine, London, United Kingdom, Institute of Global Health, University of Heidelberg, Germany, Li Guangqian Medical School, Singapore, Calvin J Chiew, National Health System of Singapore, and Vernon J Lee, Surrey School of Public Health, National University of Singapore Dr. Smith is the corresponding author of the article, who went deep into the SARS front line in 2003.

Similarities and differences between the two outbreaks

In November 2002, severe acute respiratory syndrome coronavirus (SARS-CoV) appeared in China and spread rapidly, causing global panic. As of July 2003, more than 8,000 SARS cases have been detected in 26 countries around the world.

17 years later, in December 2019, a new coronavirus SARS-CoV-2 appeared in Wuhan, China, and led to the rapid spread of 2019 coronavirus disease (Covid-19).

On January 30, 2020, Covid-19 was declared a public health emergency of international concern.

The authors mention that the similarity between SARS-CoV and SARS-CoV-2 is striking, and this similarity is not just in naming.

The entire genome of SARS-CoV-2 is 86% similar to SARS-CoV. Both viruses have high homology with the SARS-like coronavirus isolated from bats, which indicates the same as SARS-CoV SARS-CoV-2 also originated from bats.

In addition, the source of both outbreaks is believed to be related to a trading market that sells a variety of wild animals and livestock.

Even in terms of disease transmission, the two viruses share clear similarities. Although two viruses have been reported to spread the virus through feces, the main route of transmission is still respiratory droplets.

Angiotensin-converting enzyme 2 (ACE2) found in the human lower respiratory tract has been identified as both SARS-CoV and SARS-CoV-2 entry cell receptors.

It is known that the median latency of Covid-19 and SARS is about 5 days. The median interpersonal transmission of Covid-19 was 7.5 days, and the initial estimate of the number of basic infections (R0) was 2.2.

The median interpersonal transmission of SARS was 8.4 days, and the R0 range was 2.2-3.6.

The risk factors for the outcomes of these two serious diseases are old age and comorbidities.

In addition, the patient's progression followed a similar pattern, with acute respiratory distress syndrome progressing approximately 8-20 days after the onset of the first symptom, and pulmonary abnormalities on chest CT showed the most severe approximately 10 days after the first symptom occurred.

However, the authors mention that the similarities end here, and that the trajectory of the epidemic looks different.

A total of 8,098 SARS cases were reported in 2003, including 774 deaths, which were eventually brought under control in July 2003 within 8 months.

Although cases were reported in 26 countries, the vast majority of cases were concentrated in China, Singapore, and Toronto, Canada.

SARS was eventually brought under control by monitoring symptoms, rapidly isolating patients, strictly controlling all contacts, and implementing first-level quarantine in some areas.

In other words, SARS has been effectively cleared by blocking human-to-human transmission.

In contrast, as of February 28, 2020, more than 82,000 confirmed cases have been reported in the two months after the start of the Covid-19 epidemic, with more than 2800 deaths, most of them in China. With the exception of China, more than 3,600 cases have been reported in 46 countries.

The authors raise questions: Traditional public health measures are widely used to clear SARS, but can Covid-19 be controlled by these same measures?

In their opinion, it was important to analyze what was being done at the time and what lessons were applicable to Covid-19.

Extensive public health measures implemented during SARS

The authors mention that in the absence of vaccines and symptomatic treatments, the only public health tools to control infectious diseases are quarantine, quarantine, social alienation and community blockades.

Isolation is to separate the patient from the uninfected person and is usually done in a hospital, but patients with mild infection can also be done at home.

The authors mention that for quarantine to be successful, case detection should be done early, either before the start of viral excretion or at least before the peak of viral excretion begins.

For SARS, the viral load peaks a few days after onset, 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, the focus is on fever or respiratory symptoms, as well as epidemiological links (contact or travel history).

For example, during SARS, the secondary family transmission rate in Singapore was low (6.2%), indicating the need for rapid patient detection and isolation.

Similarly, in Toronto, Canada, the secondary family transmission rate is 10%. It is worth noting that the secondary sexual transmission rate is linearly related to the time spent at home after the onset of index patient symptoms.

In addition, health care-related transmission in Singapore accounts for more than 90% of all cases. Once comprehensive measures are taken, almost all patients are quickly quarantined before secondary sexual transmission occurs.

They mentioned that the SARS epidemic in Singapore was transmitted by 5 super transmission events, 3 of which were caused by patients who did not initially show 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 the quarantine period.

The prerequisite for successful quarantine is the rapid and comprehensive tracking of every contact with a confirmed patient. Isolation can be done at home or at designated locations such as hotels, both of which were used during the SARS epidemic.

The principle is that if the quarantined person develops disease, it will be guaranteed that he will not spread the disease through any close contact, thereby effectively reducing the R0 of the epidemic to less than 1.

The authors cited strong examples during this SARS period. For example, Toronto Public Health investigated 2,132 suspected SARS cases and determined that 23,103 contacts need to be quarantined, and close contacts were quarantined according to law. Hong Kong, the police conducted random checks; In Singapore, cameras are installed in each contact's home.

Once all infected people and their contacts cannot be identified, the next step may be to implement control measures across the community. Community-wide control is an intervention that applies to the entire community, city, or region, and aims to reduce personal interaction. These interventions include encouraging individuals to take responsibility for identifying diseases, increasing social distance between community members, including eliminating public gatherings, and finally implementing community isolation. Because of the large number of people involved, implementing control measures at the community level is more complicated than quarantine or quarantine.

The authors mention that China is the best example of such a large-scale isolation. In April 2003, China comprehensively controlled all activities against SARS by formulating national-level, clear, reasonable, and widely implemented guidelines and control measures.

Tight controls include school suspensions, closures of public places, and the cancellation of the May Day holiday.

The immediate effect is that R0 drops sharply and continues.

Singapore has become a so-called "thermometer country": schools mandate temperature monitoring and temperature screening at the entrance to public places.

Hundreds of fever clinics have been opened, and mass media have been used to encourage people to check their fever multiple times a day, and case detection has been further improved.

The authors mentioned that, in general, citizens with higher levels of anxiety, greater awareness of SARS, and higher-than-average risk perception capabilities are more likely to take comprehensive preventive measures to combat infection.

The public's awareness of SARS is very high, and they are very willing to undergo quarantine when needed (in a psycho-behavioral study conducted in Singapore and Hong Kong, 90% of the respondents expressed their willingness).

And all countries affected by SARS also have 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 implementation of personal protection for medical staff, and restrictions on visitor and medical staff activities.

Negative pressure chambers were basically not used at that time, or only when they were available. All hospitals have strengthened their infection control precautions, including providing separate shunting facilities for patients with fever or respiratory symptoms.

In Toronto and Singapore, medical staff are required to use gloves, protective clothing, eye masks, and N95 masks at the time of admission, regardless of whether the contact is a SARS patient.

To reduce in-hospital transmission, hospitals are prohibited from visiting patients with SARS unless they are based on compassion. Health care workers or visitors who have been exposed to SARS transmission facilities are not allowed in non-SARS areas.

In Singapore, all health care workers are required to take temperature tests twice a day.

Health care workers who have fever symptoms must report to a designated health care facility and be quarantined until the possibility of SARS is ruled out.

It is worth mentioning that in order to accommodate a large number of SARS patients (including possible and suspected), Beijing quickly built a 1,000-bed "Xiaotangshan Hospital" in one week, which has treated 1/7 of the country within 2 months Of SARS patients.

What is the difference between 2020 and 2003?

The authors wrote in the article: 17 years later, we can learn from SARS.

In fact, the time from Covid-19 discovery to virus sequencing and diagnosis development was much faster than during SARS, and diagnostic tests were available worldwide in two weeks after the case was reported in China.

In addition, the Global Outbreak Alert and Response Network (GOARN), the Epidemic Prevention and Innovation Alliance (CEPI), the Global Cooperative Research and Prevention Organization for Infectious Diseases, etc., can accelerate the outbreak response and quickly launch technology platforms to develop vaccines and therapies.

The article mentions that China now has higher medical standards, better educated health care personnel, and more technical and scientific expertise than in 2003.

China's current response is more transparent and decisive. It has already begun operations in the early stages of the current outbreak, much earlier than in 2003 when SARS occurred.

So, by January 30, 2020, the Covid-19 case has surpassed SARS? The authors list several possible explanations.

First, the situation is different. Controlling Wuhan, the center of Covid-19, is challenging under many factors.

Wuhan is the largest city in Central China (with a population of 11 million). It is a major transportation hub and industrial and commercial center in Central China. It has the largest railway station, the largest airport, and the largest deep-water port in Central China.

Over the past 10 years, China's outbound tourism has more than doubled, and urban population density may even have tripled. In big cities like Wuhan, people's proximity in living, commuting, and working environments magnifies the spread of people.

The huge population size is the biggest challenge. The hospital was initially overwhelmed by too many patients, and many patients were not hospitalized because of insufficient beds, which exacerbated community transmission.

To make matters worse, just a few days before Wuhan's "closed city", due to the proximity of the Spring Festival, more than 5 million people (many of whom may be carriers of the virus) left the city, which is why Covid-19 spread to Other provinces.

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 peak viral excretion occurs when patients already have severe respiratory symptoms and can be easily identified.

In contrast, preliminary evidence suggests that Covid-19 has begun to spread at an early stage.

This means that it is too late for Covid-19 patients to be isolated when their condition is more severe. The effectiveness of isolating and tracking contacts at this time depends on the proportion of transmissions that occur before symptoms appear. Pre-symptom transmission also discounts the effectiveness of temperature screening.

The third explanation is that Covid-19 may have a higher transmission capacity than SARS. R0 is a central concept in the epidemiology of infectious diseases, and it represents the number of subsequent cases caused by an infection in the absence of protective measures.

An article published by Smith and his collaborators in the Journal of Travel Medicine on February 13 pointed out that the average R0 of Covid-19 is 3.28 and the median R0 is 2.79, which is higher than SARS.

Of course, the authors believe that a more accurate R0 can only be determined when the epidemic is stable.

There is no doubt that the speed of Covid-19 transmission, that is, 80,000 cases from the first case in early December 2019 to the end of February 2020, is obviously faster than SARS between March 2002 and March 2003. SARS is even here There is no control of any kind during the period.

As another example, as of February 28, 2020, despite public health measures, more than 700 of the approximately 3,700 passengers and crew on the Japanese Diamond Princess cruise ship were infected. This high infection rate indicates that it is extremely contagious high.

The fourth explanation is that the clinical scope is different. The authors point out that the initial definition of cases in China focused on pneumonia, and based on this narrow case definition, the reported initial case fatality rate (CFR) was about 10%.

However, as the epidemic progressed, it became clear that mild cases were common among patients with Covid­-19.

But even with more sensitive surveillance systems, patients with mild disease manifestations are missed, and these patients may spread the disease silently, just like the flu.

It is worth noting that even if the mortality rate of Covid-19 (probably <2%) is ultimately much lower than the mortality rate of SARS (10%), this is still not reassuring.

Because high infectivity leads to more cases, the final death toll will also be higher than SARS.

The fifth explanation is that community transmission is more pronounced. SARS is mainly transmitted in hospitals, but for Covid-19, widespread community transmission is already apparent.

As of February 28, 2020, more than 82,000 cases have 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 contacts who subsequently develop into infected people are not isolated and receive proper medical observations.

Therefore, China has decided to implement the most severe of all traditional public health measures: community segregation reduces social distance, uses masks, and blocks public transportation in Wuhan, including buses, trains, ferries and airports.

The authors mention that China has implemented the largest quarantine in history to prevent the epidemic from spreading to other parts of the world. As of January 30, 2020, a total of 1,135,79 close contacts have been tracked, and 102,427 people have received medical observation.

They wrote, "This approach is an unprecedented gigantic effort that surpasses all efforts done during SARS."

Will the same measures succeed? 

The authors mention that the price behind these huge efforts is travel and trade, which has caused losses to China's economy and other fields. The reason for these sacrifices is that their memory of SARS has ignited hope that the epidemic will be contained.

But will these strict measures really be as successful as they were during the SARS period? The authors believe that this depends on the extent of transmission of subclinical cases (asymptomatic or mild symptoms), including the peak excretion 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 believe that before these answers are known, the political and medical communities need to use existing tools to continue taking control measures. "China should be commended for its political will in implementing what might appear to be extreme measures. Undoubtedly, no other country could enact what China is currently doing."

It is currently known that even if the country has the political will to detect cases quickly, isolate patients quickly, comprehensively track contacts, and immediately isolate all contacts, then even exporting cases to these countries may not necessarily lead to rapid large-scale outbreaks outbreak.

Controlling Covid-19 should be the current focus. The authors emphasize that the short-term costs of control will be much lower than the long-term costs of uncontrol. However, closing institutions and public places and restricting travel and trade cannot be sustained indefinitely.

They argue that countries must face the reality that, in the long run, individual case control may not be possible and that control needs to be shifted to mitigation to balance the costs and benefits of public health measures.

The authors say that even though our public health measures cannot completely control the spread of Covid­-19 because of the nature of the virus, they will still effectively delay widespread community-borne transmission, thereby reducing the peak incidence and its impact on public services.

In addition, by expanding the size of the health system and improving response decisions, the size of outbreaks can be minimized, or peaked, global deaths can be reduced, and of course global transmission can be slowed before an effective vaccine is available.

Source: The Lancet Infectious Diseases, The Paper

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