24 asymptomatic new coronary infections study: infection period of up to 29 days

According to the available data, 189 of the 1,723 tourists tested on the Diamond Princess cruise ship were asymptomatic new coronavirus infections. This clearly suggests that there are a large number of asymptomatic infections or mild symptoms in the population, but they are not detected.

Recently, researchers from Nanjing Second Hospital (Nanjing Hospital affiliated with Nanjing University of Traditional Chinese Medicine), Nanjing Medical University and other teams published a study online on the pre-printed platform medRxiv, “The clinical characteristics of 24 patients with asymptomatic new coronavirus infection in close contacts in Nanjing area.” The researchers say identifying and isolating asymptomatic infections and mild symptoms is key to half-phase prevention and control of the outbreak.

Many previous studies have reported on the clinical characteristics of patients with new coronary pneumonia, as well as evidence of human-to-human transmission. Genetic analysis of the new coronavirus shows that the virus is similar to SARS-CoV, but the difference is that the new coronavirus is already a mobile source of infection when the patient is still in the incubation period and is active as usual, which causes the virus to spread further.

It is worth noting that, to date, data on asymptomatic infections in the country are limited. The research team conducted an epidemiological survey of all close contacts of new coronaviruses in hospitals and communities between January 28 and February 9 in Nanjing, Jiangsu Province, and studied the clinical characteristics of 24 asymptomatic infections tested positive for neo-coronavirus by pharynx swab nucleic acid, while describing the potential for viral transmission of asymptomatic infections.

The team noted that all the asymptomatic carriers they found were admitted to Nanjing Second Hospital, so the samples were highly representative in Nanjing. They suggest that active contact tracking and strict health monitoring should remain important prevention and control strategies in China and around the world, as large-scale rework is under way.

In addition, since nucleic acid detection is not uncommon in patients, the team emphasizes that new coronary patients who have been discharged from the hospital should be isolated and multiple viral nucleic acid tests should be performed.

Asymptomatic infections have mild symptoms, and nucleic acid testing is essential for identifying young people

24 asymptomatic new coronary infections study: infection period of up to 29 days

Basic information for 24 asymptomatic infections, blue box for time in Hubei, solid brown triangle for nucleic acid test positive, hollow brown triangle for nucleic acid test negative

The paper shows that there are no medical personnel in the case, of which 8 cases (33.3%) have a recent history of exposure to Hubei (cases 1 and 5 are Hubei residents, cases 3, 4, 6, 9, 13 and 17 have been to Hubei), their time period in Hubei may be suspected contact time. According to epidemiological investigations, the suspected exposure time of other cases withno history of exposure in Hubei was marked with a gray box. The date of diagnosis for each case indicates a decrease in the number of cases visited to Hubei since 28 January 2020.

Among the cases surveyed were asymptomatic infections of neo-coronavirus esfound sons of all ages, ranging from 5 to 95 years (median age 32.5 years), while 20.8 per cent (5/24) were under the age of 15. There were 8 male cases (33.3 per cent), 2 cases with a history of smoking (cases 1 and 13), and 2 cases diagnosed with diabetes and hypertension (cases 8 and 13).

Five cases (cases 2, 4, 5, 6 and 10) developed symptoms during hospitalization.

All five cases were feverish, fearless and cold, with a temperature that fluctuated between 36.5 c-38.0 degrees C, but no cases had a high fever (body temperature; 39 degrees C). Cases 4, 6 and 10 have no other symptoms other than fever. Case 2 also includes cough, fatigue and nasal congestion;

Several cases also showed brief symptoms during hospitalization, including chills (cases 8), diarrhoea (cases 21 and 22) and rashes (cases 16 and 18), but these symptoms have been discussed by a clinical panel of experts and are considered to be intravenous immunoglobulin responses. These side effects were caused by Lofinave/Litonavir and Dalunawe/Corbis, respectively.

Therefore, the above cases are not classified as cases of symptoms caused by the new coronavirus.

At the time of admission, chest CT scans were performed in all 24 cases. Twelve of these cases (50.0%) showed typical chest CT images of new coronary pneumonia, i.e. a glass or patchy shadow of the lungs. Five cases (20.8%) showed striped shadows in the lungs, an atypical image. The remaining 7 cases (29.2%) had normal CT scans.

In 4 of the 24 cases (16.7%) there was a decrease in lymphocytes (less than 0.8 x 109 cells/L) upon admission to the hospital. Leuketa reduction was also observed in 4 cases, with leukocyte reduction during hospitalization during hospitalization in cases 2 and 5. Elevated symptoms of alanine transaminase, temporine transaminase, creatine kinase, C-reactive protein, and D-dipolymer levels are not common.

In 7 patients, serum lactose dehydrogenase levels were elevated, and 3 of them were accompanied by elevated Levels of C-reactive protein.

Overall, these asymptomatic cases were less severe than previously reported in Wuhan, Hubei Province.

Notably, the team found that even during hospitalization, young cases were more likely to become asymptomatic patients and that CT images were normal. This part suggests that nucleic acid testing is essential for identifying asymptomatic infections in young close contacts.

There is the phenomenon of fuyang, there are cases of infection period has been more than 29 days

Twenty-one patients (87.5%) received antiviral treatment in the initial treatment, including 1 antibiotic, antifungal and immunoglobulin therapy, and 2 patients receiving immunoglobulin therapy.

All of these cases were treated with interferon atomization, none of which had severe pneumonia, and therefore did not require systemic hormone therapy, mechanical ventilation or access to the ICU, and none of the deaths.

As of February 18, 2020 (the paper’s cut-off), a total of 18 cases (75.0%) of patients had been removed from the virus (2 nucleic acid tests were continuously negative), 9 of which had been discharged from the hospital and the remaining 9 remained in the hospital for further observation.

In six cases (cases 3, 8, 13, 16, 19 and 23) the nucleic acid test results were negative and reversed to positive.

Of particular concern is that case 18 is positive again, even after two consecutive negative nucleic acid tests.

Five cases (cases 7, 9, 11, 14 and 24) cleared the virus within a short period of time.

The authors define the period of infection as the interval from the first day of the patient’s nucleic acid positive to continuous negative. The study concluded that the infection period ranged from 1 to 21 days (median: 9.5 days, and IQR 3.5-13.0 days).

It is worth noting, however, that because six patients did not have test data and the exact date of the first infection was uncertain, the above-mentioned duration of infection may have been underestimated and the actual duration of infection was longer than calculated.

In particular, case 13 asymptomatic infections were still positive for the neo-coronavirus until 18 February 2020, indicating that the infection period could be as long as 29 days (from 21 January to 18 February 2020).

The researchers found that seven patients (29.2%) had normal CT images and no symptoms during their stay in hospital. These seven cases were younger than other cases (median age 14.0). CT showed no difference in other characteristics of normal and abnormal two groups of asymptomatic patients, which the authors believe may be due to a limited sample size.

None of the seven patients had significant abnormalities in their blood tests. The median infection period of these seven patients was 4.0 days.

As of 18 February 2020, none of the 24 cases had developed severe pneumonia, and only five had shown typical symptoms during hospitalization. Similar to previous studies, fever, cough and fatigue are the main symptoms. Lymphocytes and white blood cells that previously represented the severity of the disease were not common in asymptomatic cases studied.

Family transmission in case 13: evidence of transmission by carriers of asymptomatic new coronavirus

24 asymptomatic new coronary infections study: infection period of up to 29 days

Case 13 family transmission schematic, yellow box represents incubation period, pink box indicates symptom appearance period

The team examined the medical and epidemiological histories of each confirmed or suspected neo-coronavirus infection and family members.

In the family with case 13, the family 1 (the wife of case 13) went to the hospital first.

The family member is a 64-year-old woman who was in good health but has a fever (up to a maximum temperature of 38.7 degrees Celsius) on 30 January 2020 and has cough, fatigue and vomiting symptoms. Three days later (2 February 2020), she went to the hospital and tested positive for the new coronavirus. The hospital then conducted epidemiological investigations and nucleic acid tests on her son (family 2), daughter-in-law (family 3) and case 13.

Family 2 and Family 3 both had respiratory symptoms before the examination and were eventually diagnosed with new coronary pneumonia. The nucleic acid test for case 13 also tested positive, but he was admitted to hospital without any symptoms. In the epidemiological investigation, case 13 indicated that he had travelled to Huanggang City, Hubei Province, from 19 January to 20 January 2020.

Family 1, Family 2 and Family 3 are local residents of Nanjing, and said that in the last 14 days, except for the exposure of case 13, there is no history of contact with any confirmed or suspected new coronary pneumonia patients.

Of the three infected family members, family members 1 developed severe symptoms of new coronary pneumonia and were admitted to the ICU on 6 February 2020. Family 2 and Family 3 were cleared of the virus on 18 February 2020.

Overall, asymptomatic case 13 of the carrier of the new coronavirus transmitted the virus to his family members, one of whom developed severe new coronary pneumonia and was sent to the ICU.

These findings suggest that asymptomatic carriers can cause human-to-human transmission and should be considered a source of neo-coronavirus infection.

Therefore, the team stressed that multiple nucleic acid screening, strict monitoring of close contacts, and thus containing the potential outbreak of the outbreak has important public health implications. Guidance for self-protection, active isolation of close contacts, whether at home or centralized, should also be constantly emphasized.

The study also recommends that new coronapatients who have been discharged from the hospital should be isolated and tested for multiple viral nucleic acids.

Of course, there are small sample sizes in the study, and the team believes that a large-scale multicenter study is needed to validate the findings.

(Original title: 24 asymptomatic new coronary infections study: infectious, the maximum infection period of more than 29 days)

Journalist He Liping Zhang Rujuan