Do children spread COVID19?

[HughParsonage]

Lots of conflicting intuition on this one. Do they spread it more? less? at all?

[wfmackey]

Will look into properly today.

[wfmackey]

Sorry I have been distracted today. Will get to this tomorrow morning.

[wfmackey]

Evidence is limited. (I will update this with some more tonight)

• Children appear to spread it less than adults -- both to other children and to adults.
• Children are also less likely to be the index case in a household than adults, and than children in otherwise similar viruses.
• Definitely get it less than adults.
• Children are not likely to be asymptomatic. In China: (~2-5% of confirmed cases, decreasing with age); are most likely to have mild (~50%) or moderate (30%) symptoms [Dong et al]. Zero asymptomatic children found in Iceland or Netherlands.

Children and COVID-19 transmission studies

Danis et al: French Alps case study

Danis, K., Epaulard, O., Bénet, T., Gaymard, A., Campoy, S., Bothelo-Nevers, E., … Team, I. (2020). Cluster of coronavirus disease 2019 (Covid-19) in the French Alps, 2020. Clinical Infectious Diseases. https://doi.org/10.1093/cid/ciaa424

Date: 11 April Data: index case study starting in French Alps

The index case stayed 4 days in the chalet with 10 English tourists and a family of 5 French residents; SARS-CoV-2 was detected in 5 individuals in France, 6 in England (including the index case), and 1 in Spain (overall attack rate in the chalet: 75%). One pediatric case, with picornavirus and influenza A coinfection, visited 3 different schools while symptomatic. One case was asymptomatic, with similar viral load as that of a symptomatic case. Seven days after the first cases were diagnosed, one tertiary case was detected in a symptomatic patient with a positive endotracheal aspirate; all previous and concurrent nasopharyngeal specimens were negative. Additionally, 172 contacts were monitored, including 73 tested negative for SARS-CoV-2.

The occurrence in this cluster of one asymptomatic case with similar viral load as a symptomatic patient, suggests transmission potential of asymptomatic individuals. The fact that an infected child did not transmit the disease despite close interactions within schools suggests potential different transmission dynamics in children. Finally, the dissociation between upper and lower respiratory tract results underscores the need for close monitoring of the clinical evolution of suspect Covid-19 cases.

Zhu et al: household clusters internationally

Zhu, Y., Bloxham, C. J., Hulme, K. D., Sinclair, J. E., Wei, Z., Tong, M., … Short, K. R. (2020). Children are unlikely to have been the primary source of household SARS-CoV-2 infections. https://doi.org/10.1101/2020.03.26.20044826

Date: 30 March

Data: 31 households with clusers from international literature

Drawing on studies from China, Singapore, South Korea, Japan, and Iran a broad range of clinical symptoms were observed in children. These ranged from asymptomatic to severe disease. Of the 31 household transmission clusters that were identified, 9.7% (3/31) were identified as having a paediatric index case. This is in contrast other zoonotic infections (namely H5N1 influenza virus) where 54% (30/56) of transmission clusters identified children as the index case.

Whilst SARS-CoV-2 can cause mild disease in children, the data available to date suggests that children have not played a substantive role in the intra-household transmission of SARS-CoV-2.

Ministry of Health: Netherlands

National Institute for Public Health and the Environment. (2020). Children and COVID-19.

Date: April Data: admin and surveys of Dutch households

RIVM research into the reports shows that the spread of COVID-19 mainly takes place between persons of approximately the same age. This is based on data from patients with symptoms and concerns people between 40 and 80 years. Children are less likely to be infected by adults. When this does happen, it turns out that it is mainly in the home situation. Patients under 20 years play a much smaller role in the spread than adults and the elderly.

Around 40 GP practices in the Netherlands register the number of patients visiting the practice with flu-like complaints, through the NIVEL testing stations . A culture from the nose and throat is taken from some of these patients, which is examined in the laboratory to detect viruses, such as COVID-19. In total, 6.5% of them turned out to be infected. This percentage was highest in week 14 with 30%. In the last weeks the percentage was about 15-20%. No infection was found in the patients under 20 years of age who were tested. This confirms the current understanding that children are less likely to be infected and become ill than adults.

RIVM National Institute for Public Health and the Environment set up a study in a short period to find out more about COVID-19 infected people and their family contacts. Families participate in this study in collaboration with GGD Utrecht. Up until mid April, a total of 54 households with a total of 239 participants, 185 of whom are housemates are participating. This involves 123 adults and 116 children between the ages of 1 and 16. Although the study is still ongoing, there are already preliminary results. There are no indications that children younger than 12 years were the first to be infected within the family. Children who were found to be infected with COVID-19 had fewer symptoms than adults. Respiratory complaints, such as sore throats, coughs and nasal colds, were also less common in children than in adults.

Gudbjartsson et al: Iceland

Gudbjartsson, D. F., Helgason, A., Jonsson, H., Magnusson, O. T., Melsted, P., Norddahl, G. L., … Stefansson, K. (2020). Spread of SARS-CoV-2 in the Icelandic Population. New England Journal of Medicine, NEJMoa2006100. https://doi.org/10.1056/NEJMoa2006100

As of April 4, a total of 1221 of 9199 persons (13.3%) who were recruited for tar- geted testing had positive results for infection with SARS-CoV-2. Of those tested in the general population, 87 (0.8%) in the open-invitation screening and 13 (0.6%) in the random-population screening tested positive for the virus.

Children under 10 years of age were less likely to receive a positive result than were persons 10 years of age or older, with percentages of 6.7% and 13.7%, respectively, for targeted testing; in the population screening, no child under 10 years of age had a positive result, as compared with 0.8% of those 10 years of age or older.

Key: There is no evidence out of Iceland of asymptomatic children with COVID-19. Random sampling of the population found that children (under 20) were less likely to be COVID-19 positive than adults, with no children under 10 testing positive.

Dong et al: China

Dong Y, Mo XI, Hu Y, et al. Epidemiological characteristics of 2143 pediatric patients with 2019 coronavirus disease in China. Pediatrics. 2020;16:16

Children are not likely to be asymptomatic (~2-5% of confirmed cases, decreasing with age); most likely to have mild (~50%) or moderate (30%) symptoms.

Table (2) Age Group,	Asymptomatic, n (%)	Mild, n (%)	Moderate, n (%)	Severe, n (%)	Critical, n (%)	Total, n
<1	7 (1.9)	204 (54.2)	125 (33.2)	33 (8.8)	7 (1.9)	376
1–5	15 (3.1)	245 (49.9)	195 (39.7)	34 (6.9)	2 (0.4)	491
6–10	30 (5.8)	277 (53.3)	191 (36.7)	22 (4.2)	0 (0.0)	520
11–15	27 (6.5)	198 (48.1)	170 (41.3)	14 (3.4)	3 (0.7)	412
>15	15 (4.5)	164 (49.1)	145 (43.4)	9 (2.7)	1 (0.3)	334
Total	94 (4.4)	1088 (51.0)	826 (38.7)	112 (5.3)	13 (0.6)	2133

Qiu et al: Zhejiang, China

Qiu, H., Wu, J., Hong, L., Luo, Y., Song, Q., and Chen, D. (2020). Clinical and epidemiological features of 36 children with coronavirus disease 2019 (COVID-19) in Zhejiang, China: an observational cohort study. The Lancet Infectious Diseases. https://doi.org/10.1016/S1473-3099(20)30198-5

Date: 25 March

Data: Paediatric patients (aged 0–16 years) with confirmed COVID-19 from electronic medical records in three hospitals in Zhejiang, China.

Key: Large proportion of children with COVID-19 are asymptomatic. The route of transmission for almost all children was by close contact with family members.

The route of transmission was by close contact with family members (32 [89%]) or a history of exposure to the epidemic area (12 [33%]); eight (22%) patients had both exposures

Although all paediatric patients in our cohort had mild or moderate type of COVID-19, the large proportion of asymptomatic children indicates the difficulty in identifying paediatric patients who do not have clear epidemiological information, leading to a dangerous situation in community-acquired infections.

Lee et al: comment

Lee, P. I., Hu, Y. L., Chen, P. Y., Huang, Y. C., and Hsueh, P. R. (2020). Are children less susceptible to COVID-19? Journal of Microbiology, Immunology and Infection. https://doi.org/10.1016/j.jmii.2020.02.011

Date: February 25

Data: None

The reasons for the relative resistance of children to some infectious diseases remains obscure. It was suggested that maturational changes in the axonal transport system may explain the relative resistance of immature mice to poliovirus-induced paralysis. Other suggested reasons include children having a more active innate immune response, healthier respiratory tracts because they have not been exposed to as much cigarette smoke and air pollution as adults, and fewer underlying disorders. A more vigorous immune response in adults may also explain a detrimental immune response that is associated with acute respiratory distress syndrome.

Kelvin & Halperin: comment

Kelvin, A. A., and Halperin, S. (2020). COVID-19 in children: the link in the transmission chain. The Lancet Infectious Diseases. https://doi.org/10.1016/S1473-3099(20)30236-X

Date: 25 March

Data: None

Key: Children can get COVID-19 and are often symptomatic, meaning they could be facilitators of the virus.

Infants and young children are typically at high risk for admission to hospital after respiratory tract infection with viruses such as respiratory syncytial virus and influenza virus. Immaturity of the respiratory tract and immune system is thought to contribute to severe viral respiratory disease in this age group. Therefore, the absence of paediatric patients with COVID-19 has perplexed clinicians, epidemiologists, and scientists. Case definitions and management strategies for children are absent because of the limited number of paediatric patients with COVID-19.

The most important finding to come from [Qiu et al] is the clear evidence that children are susceptible to SARS-CoV-2 infection, but frequently do not have notable disease, raising the possibility that children could be facilitators of viral transmission. If children are important in viral transmission and amplification, social and public health policies (eg, avoiding interaction with elderly people) could be established to slow transmission and protect vulnerable populations. There is an urgent need to for further investigation of the role children have in the chain of transmission.

Sidenote on adult transmission:

Asymptomatic Transmission, the Achilles’ Heel of Current Strategies to Control Covid-19: https://www.nejm.org/doi/full/10.1056/NEJMe2009758?query=recirc_mostViewed_railB_article

[HughParsonage]

Very strange. Supplementary: are there any other viruses known to be weakly spread by children?

[wfmackey]

Yeah I heard something about TB -- let me track it down.

[wfmackey]

Tuberculosis (TB) in Children

TB is caused by bacteria. It’s most often caused by Mycobacterium tuberculosis (M. tuberculosis). Many children infected with M. tuberculosis never develop active TB and remain in the latent TB stage.

Latent TB infection. This occurs when a child has TB bacteria in his or her body, but does not have symptoms. The infected child’s immune system causes the TB bacteria to be inactive. For most people who are infected, the TB will be latent for life. This child would have a positive skin test but a normal chest X-ray. He or she can't spread the infection to others.

Some are connecting the dots and testing the TB vaccine for COVID! https://www.livescience.com/coronavirus-protection-using-tuberculosis-vaccine.html

[wfmackey]

Re kids in school: given the lack of conclusive international evidence (although it does seem to sway towards low transmission from kids), should we use the figures from the NSW study to determine the probability of transmission in school?

http://ncirs.org.au/sites/default/files/2020-04/NCIRS%20NSW%20Schools%20COVID_Summary_FINAL%20public_26%20April%202020.pdf

[wfmackey]

New Lancet paper out a few hours ago asserts that kids have the same attack rate and lower rates of fever with COVID-19 than adults under 60: https://www.thelancet.com/action/showPdf?pii=S1473-3099%2820%2930287-5

@HughParsonage this paper is worth a look re default set_epipars()

[HughParsonage]

Thanks. A few thoughts:

• Looks at how the virus is transmitted during the lockdown. (Lockdown commenced Jan 23, study was tracked from Jan 14.)
• Refers to 'attack rate' rather than reproduction number, which seems a useful parameters. The attack rate is the expected number of people an infected person will infect. They estimate 11.2% attack rate among household members(!), 6.6% for general population, and find little difference in the attack rate between ages.

[wfmackey]

Sidenote: I can't work this out: https://www.nytimes.com/reuters/2020/04/25/us/25reuters-health-coronavirus-prisons-testing-insight.html

Asymptomatic rates that high are incompatible with other literature (eg Iceland). But it's an enormous sample. I guess we'll have to wait until they publish something about it rather than just feeding comments to the media?

Age could have something to do with it.