What are the differences between COVID-19 and the flu epidemic?
The epidemic caused by the new Coronavirus (2019-nCoV) is still spreading. This disease, which has just been officially named COVID-19, has caused more than 40,000 infections and more than 1,000 deaths. At the same time, on the other side of the ocean, another epidemic also attracted people's attention. The flu season in the United States is on schedule.
According to data released by the US Centers for Disease Control and Prevention, as of February 1, 22 million to 31 million people are expected to be infected during the flu season, and the number of patients dying from influenza is between 12,000 and 30,000.
Seeing such figures, some readers may be surprised when they think:
Is the flu epidemic in the United States worse?
What are the differences between COVID-19 and the flu epidemic?
Is this really the case? What are the differences between COVID-19 and the flu epidemic?
The facts are being unraveled below:
1. Unknown risk
Influenza viruses (including influenza A and B viruses) and 2019-nCoV are viruses that can cause respiratory diseases.
It should be reminded that although the flu is called influenza, it has a far-reaching relationship with the common cold. Influenza is caused by a special type of influenza virus.
Compared with the common cold, its pathogenic source is different, so it has a more infectious and higher lethal rate.
In the field of public health, the biggest difference between the two is the degree of human cognition. Scientists have studied the flu virus for decades.
So although the flu is dangerous, we have a good understanding of flu treatment, symptoms and possible flu outbreak season.
In contrast, we know very little about 2019-nCoV because it is a completely new virus.
This also means that no one knows about its future spread, the number of deaths caused, and the final result of the epidemic.
This unknown is also one of the sources of our fear.
Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID), said at the White House press conference:
"Although the incidence and death toll from influenza are also high, we have figured out the flu The regularity of outbreaks. I can assure you that the number of influenza patients will decrease by March and April.
In fact, we can predict the approximate range of seasonal influenza mortality and hospitalizations very accurately. But the problem now lies, 2019-nCoV still has a lot of unknowns."
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In addition, the two viruses also have many differences in virus transmission, clinical symptoms and treatment. For 2019-nCoV, scientists are racing to discover more information.
In this process, our understanding of this virus and its threats will change accordingly. Therefore, the next description and discussion of 2019-nCoV is based on the information known so far.
2. Infectious ability
An important reason for the rapid spread of the COVID-19 epidemic is the powerful infectious ability of 2019-nCoV. Scientists often use the "basic infection number" (R0) to assess the difficulty of virus transmission.
In layman's terms, it is an assessment of how many people can be transmitted to a patient who is infected with an infectious disease.
The higher the R0 value, the stronger the infectious ability of this infectious disease.
According to the New York Times report, the R0 value of influenza virus is about 1.3.
For the R0 of 2019-nCoV, the researchers are still working hard to determine.
A study published in the New England Journal of Medicine (NEJM) on January 29 estimated that the R0 value of the new coronavirus was about 2.2.
But just today, a paper published on the preprint website analyzed nearly 9,000 cases and pointed out that the R0 of 2019-nCoV reached 3.77.
In other words, on average, each infected person can transmit the virus to 3.77 people.
If this conclusion is confirmed, it means that the contagious ability of 2019-nCoV is far higher than previously expected.
It should be noted that the R0 of each disease is not a fixed constant. R0 varies from region to region, depending on the frequency of people's contact and the intensity of epidemic prevention measures.
The length of the virus incubation period is also an important factor that affects the ability of the disease to spread.
The incubation period of influenza virus is mostly 1 to 4 days, while 2019-nCoV is more complicated.
According to a retrospective study published on the preprint website led by Academician Zhong Nanshan, the median incubation period for 2019-nCoV is 3 days, but there are significant differences between different patients:
The patient had the fastest onset of the day, and one patient claimed to have passed symptoms only appear during the incubation period of days.
Patients with a longer incubation period pose challenges to early diagnosis and isolation.
3. Mode of Transmission
The human-to-human infection of influenza virus is mainly achieved through three methods:
i. Direct transmission (also known as droplet transmission, which refers to droplets generated when a patient sneezes, coughs, or speaks, and infection caused by inhalation of people around them). ii. Aerosol spreading (droplets are mixed in the air to form an aerosol, which causes infection after inhalation) and contact spreading (droplets settle on the surface of the article, hands touch the pollution source, and then touch the mucous membranes of the mouth, nose, eyes, etc. with the hands, resulting in infection).
The influenza virus attaches to the cells in the respiratory tract, and then the hemagglutinin surface protein of the influenza virus binds to the sialic acid receptor on the surface of the human respiratory tract cells, thereby opening the "lock" of human cells, entering and infecting cell.
The method of human-to-human transmission in 2019-nCoV is also in doubt. It has been determined that the transmission route of 2019-nCoV includes direct transmission and contact transmission, and whether it can carry out aerosol transmission and fecal mouth transmission, the current evidence is still insufficient.
2019-nCoV, like SARS, enters cells through the ACE2 receptor and infects the respiratory tract.
4. Symptoms and severity
According to a report by the US Centers for Disease Control and Prevention (CDC), typical symptoms of influenza include fever, cough, sore throat, muscle aches, headache, runny or stuffy nose, fatigue, and occasional vomiting or diarrhea.
The symptoms of influenza are usually sudden, and most people infected with the flu virus will recover within two weeks. But for a small percentage of people, the flu virus can also cause other complications, such as pneumonia.
In the United States, the flu season 2019-2020 has caused 22 million to 31 million infections and 12,000 to 30,000 deaths. Therefore, the lethal rate of the flu epidemic in the United States is less than 0.1%.
In addition, so far, about 1% of the infected people in this flu season have a symptom level that requires hospitalization, which is similar to the previous flu season.
It should be pointed out that data such as the number of people infected with influenza and the number of deaths in the United States are not obtained through direct statistics, but are based on the evaluation results of the dynamic model established by the US CDC.
The model was deduced from information on the number of infections, hospitalizations, vaccination rates, high-risk cases, and deaths in 9% of the population covered by 13 influenza surveillance points across the United States.
The reason for this is that on the one hand, a large number of influenza patients may not go to the hospital or have not been tested for influenza virus.
On the other hand, some people may die due to complications caused by influenza (such as pneumonia, cardiovascular disease, etc.).
For these people, the direct cause of death in the hospital is not influenza, but influenza is the cause of death.
It can be seen from the above that the CDC's statistics on the number of influenza deaths in the United States are also broader. This partly explains that the number of deaths due to influenza in the United States reaches tens of thousands every year.
People are trying to understand the symptoms and severity of 2019-nCoV infection. Academician Zhong Nanshan's team analyzed in the latest research and pointed out that the most common symptoms of COVID-19 are fever and cough. Diarrhea, vomiting and other digestive system symptoms are extremely rare.
A previous study published in The Lancet also showed that only about 5% of patients showed symptoms of sore throat and runny nose. In contrast, COVID-19 is far more severe than the flu.
According to data released by the World Health Organization (WHO) on February 4, about 14% of the more than 20,000 patients reported in China are severely ill.
For the mortality rate of 2019-nCoV infection, we do not have exact data yet. Based on the judgment of existing research, the lethal rate of 2019-nCoV infection is about 1% to 3%, which is much higher than that of influenza.
However, with the further development of the epidemic, this number may also change.
US Secretary of Health and Human Services Alex Azar (Alex Azar) said at a news conference on January 28 that in the initial stage of the outbreak, there may be a "serious tilt" in the initially discovered cases.
In other words, most of the initially diagnosed cases may be more serious patients, which may cause the calculated mortality rate to be higher than the actual level. Aza said that as more mild patients are diagnosed, the mortality rate may decline.
5. Prevention and treatment
We can prevent 60% of seasonal flu by vaccination. Currently, the development of vaccines against COVID-19 is in progress. Some domestic and foreign teams have entered the stage of animal testing.
For example, the National Institutes of Health announced recently that a vaccine against COVID-19 is being developed, and is expected to enter the first phase of clinical trials within two and a half months.
However, it still takes a long time until the vaccine is finally released.
WHO Director General Tan Desai said on the 11th that the COVID-19 vaccine is expected to be ready within 18 months.
However, for these two diseases, the following recommendations from the US CDC are common:
- Wash your hands frequently with water and soap, and wash your hands for no less than 20 seconds.
- Do not touch the eyes, nose and mouth with unwashed hands.
- Avoid close contact with patients.
- Stay at home when you are sick, do not walk around or go to crowded areas.
- Pay attention to cleaning and disinfecting frequently touched objects or surfaces.
For influenza, people have found more effective antiviral drugs. For example, for this season's flu, the recommended drugs of the US CDC include oseltamivir, zanamivir and paramivir.
In the clinical treatment of COVID-19, intravenous antibiotics, oxygen therapy, oseltamivir and mechanical ventilation are currently the most frequently used therapies.
In addition, more severe patients received systemic glucocorticosteroid treatment. Special drugs for COVID-19 are still being sought.
The clinical trials of redoxivir are being carried out in hospitals in Wuhan. In addition, drugs such as abidol and darunavir also show potential in in vitro cell experiments.
But it will take some time before the drug is marketed through clinical testing.
6. Global epidemic
Seasonal influenza occurs every year, and is significantly different from the severity of influenza pandemic events and outbreaks of new influenza viruses.
For example, the US CDC data showed that the swine flu outbreak in 2009 was an influenza pandemic event, which is estimated to have caused about 151,000 to 575,000 deaths worldwide.
At present, the COVID-19 epidemic has not been evaluated as a global pandemic.
The reason is that most of the current cases only occur in China, and there is no outbreak in other countries or regions around the world.
Previously, the WHO declared that the COVID-19 epidemic was "a public health emergency of international concern."
This statement is mainly concerned that the virus may spread to countries with weak health systems.
The comparitive analysis of COVID19 Corona virus and Influenza like Illness flu gives the correct impression of the situation between the two.