High Secondary Attack Rate and Persistence of SARS-CoV-2 Antibodies in Household Transmission Study Participants, Finland 2020

Background Household transmission studies offer the opportunity to assess both secondary attack rate and persistence of SARS-CoV-2 antibodies over time. Methods We invited confirmed COVID-19 cases and their household members to attend up to four household visits with collection of nasopharyngeal and serum samples over 28 days after index case onset. We calculated secondary attack rates (SAR) based on the presence of SARS-CoV-2 nucleoprotein IgG antibodies (IgG Ab) and/or neutralizing antibodies (NAb) overall and per households. Three and six months later, we assessed the persistence of SARS-CoV-2 antibodies. Findings We recruited 39 index cases and 90 household members. Among 87 household members evaluated, SAR was 48% (n=42), including 37 symptomatic secondary cases. In total, 80/129 (62%) participants developed both IgG Ab and NAb, while three participants only developed IgG Ab. Among participants who had both IgG Ab and NAb during the initial follow-up, 68/69 (99%) and 63/70 (90%) had IgG Ab and NAb at 3 months, while at 6 months, 59/75 (79%) and 63/75 (84%) had IgG Ab and NAb, respectively. Participants who required hospital care had initially 5-fold IgG Ab concentrations compared to cases with mild symptoms and 8-fold compared to asymptomatic cases. Interpretation Following detection of a COVID-19 case in a household, other members had a high risk of becoming infected. Follow-up of participants showed strong persistence of antibodies in most cases. Funding This study was supported by THL coordinated funding for COVID-19 research (Finnish Government's supplementary budget) and by the Academy of Finland (Decision number 336431).

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Performance of self-collected anterior nasal swabs and saliva specimens for detection of SARS-COV-2 during symptomatic and asymptomatic periods

Open Forum Infectious Diseases ◽

10.1093/ofid/ofab484 ◽

2021 ◽

Author(s):

Carlos G Grijalva ◽

Melissa Rolfes ◽

Yuwei Zhu ◽

James Chappell ◽

Natasha Halasa ◽

...

Keyword(s):

Field Studies ◽

Kappa Statistics ◽

Non Invasive ◽

Specimen Type ◽

Household Transmission ◽

Specimen Collection ◽

Nasal Swabs ◽

Transmission Study ◽

The Difference ◽

Study Participants

Abstract Background Anterior nasal swabs (ANS) are established specimen collection methods for SARS-CoV-2 infection detection. While saliva (SA) specimens provide an alternative, few studies have comprehensively characterized the performance of SA specimens in longitudinal studies. Methods We compared SARS-CoV-2 detections between paired self-collected ANS and SA specimens from a household transmission study. Participants recorded symptoms and paired ANS and SA specimens daily for 14 days. Specimens were tested using RT-PCR. We calculated the proportion of detections identified by each specimen type among the detections from both types combined. We computed percent agreement and Kappa statistics to assess concordance in detections. We also computed estimates stratified by presence of symptoms, and examined the influence of traditional and inactivating transport media on the performance of ANS. Results We examined 2535 self-collected paired specimens from 216 participants. Among 1,238(49%) paired specimens with detections by either specimen type, ANS identified 77.1%[954](95%CI: 74.6–79.3%) and SA 81.9%[1014](79.7–84.0%), with a difference of 4.9%(1.4–8.5%). Overall agreement was 80.0% and Kappa was 0.6(0.5-0.6). Nevertheless, the difference in the proportion of detections identified by ANS and SA using traditional and inactivating transport media was 32.5%(26.8–38.0) and −9.5%(−13.7– -5.2), respectively. Among participants who remained asymptomatic, the difference in detections between SA and ANS was 51.2%(31.8–66.0) and 26.1%(0–48.5) using traditional and inactivating media, respectively. Conclusion Self-collected saliva specimens provide a non-invasive alternative to nasal swabs, especially to those collected in traditional transport media, for longitudinal field studies that aim to detect both symptomatic and asymptomatic SARS-CoV-2 infections.

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Low secondary transmission of 2009 pandemic influenza A (H1N1) in households following an outbreak at a summer camp: relationship to timing of exposure

Epidemiology and Infection ◽

10.1017/s095026881000141x ◽

2010 ◽

Vol 139 (1) ◽

pp. 45-51 ◽

Cited By ~ 7

Author(s):

T. J. DOYLE ◽

R. S. HOPKINS

Keyword(s):

Pandemic Influenza ◽

Attack Rate ◽

Influenza A ◽

Summer Camp ◽

The Novel ◽

Household Contacts ◽

Household Transmission ◽

Influenza A H1n1 ◽

Study Participants ◽

Timing Of Exposure

SUMMARYFollowing an outbreak of 2009 pandemic influenza A (H1N1) at a residential summer camp for boys aged 10–16 years, we assessed secondary household transmission of the novel virus after their return home. Of 212 study participants who attended camp, 49 had confirmed or probable influenza for a primary attack rate of 23%. Of 87 exposed household contacts who did not attend camp, only three instances of probable transmission were observed, for a household secondary attack rate of 3·5%. All secondary cases occurred in households where the ill camp attendee returned home 1 day after onset of illness, with an attack rate of 14·3% in household contacts in this category. Returning home after peak infectivity to others and advanced warning prior to reintegration of sick individuals into the household probably contributed to the overall low secondary attack rate observed.

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Household Transmission Study of Cryptosporidiosis in Bangladesh

10.1101/269985 ◽

2018 ◽

Author(s):

Poonum S. Korpe ◽

Carol Gilchrist ◽

Cecelia Burkey ◽

Emtiaz Ahmed ◽

Vikram Madan ◽

...

Keyword(s):

Young Children ◽

Attack Rate ◽

Secondary Infection ◽

High Rate ◽

Chi Square ◽

Cryptosporidium Spp ◽

Household Transmission ◽

Secondary Infections ◽

Transmission Study ◽

Duration Of Infection

ABSTRACTBackgroundCryptosporidium, an apicomplexan protozoa, is a leading contributor to diarrheal morbidity and mortality in children under five years old worldwide. As there is no vaccine and no approved drug for Cryptosporidium spp. in young children, preventing parasite transmission is crucial. We undertook a pilot case-control study to define the extent of person-to-person transmission of cryptosporidiosis within families in an urban and rural community in Bangladesh.MethodsWe enrolled 48 case families with a Cryptosporidium-infected child aged 6-18 months. Controls were age-sex matched Cryptosporidium-negative children (n=12). Once children were identified, we enrolled all household members. We then followed these individuals for 8 weeks, with weekly surveillance stools and testing with qPCR for Cryptosporidium spp.FindingsIn the 48 case families, the rate of secondary infections with Cryptosporidium was 18.6% (22/118) compared to 0 new infections (0/35) in the 12 control families. In the 22 urban Mirpur households, the secondary attack rate was 30% (18/60) in cases compared to 0% (0/14) in controls (chi-square p = 0.018). In contrast, in the 21 rural Mirzapur households, the secondary attack rate was 6.9% (4/58) in case households compared to 0% (0/21) in controls (chi-square p = 0.22). Genotyping by gp60 demonstrated infection with the same subspecies in five of six families. Serologic response to Cryptosporidium infection was associated with younger age, longer duration of infection, and C hominis gp60_IbA9G3R2 infection.InterpretationThe high rate of secondary infection in Mirpur suggests that person-to-person transmission is likely a major source of Cryptosporidium infection for young children living in this region. GP 60 genotyping demonstrated direction of infection in 2 households, and concurrent infection in five households. Further work is needed to understand the differences in parasite transmissibility and immunity to different genotypes.

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High variability in transmission of SARS-CoV-2 within households and implications for control

PLoS ONE ◽

10.1371/journal.pone.0259097 ◽

2021 ◽

Vol 16 (11) ◽

pp. e0259097

Author(s):

Damon J. A. Toth ◽

Alexander B. Beams ◽

Lindsay T. Keegan ◽

Yue Zhang ◽

Tom Greene ◽

...

Keyword(s):

Test Data ◽

Attack Rate ◽

Serological Test ◽

Close Contact ◽

Antibody Test ◽

High Variability ◽

Test Accuracy ◽

Household Transmission ◽

Wide Range ◽

Test Specificity

Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses a high risk of transmission in close-contact indoor settings, which may include households. Prior studies have found a wide range of household secondary attack rates and may contain biases due to simplifying assumptions about transmission variability and test accuracy. Methods We compiled serological SARS-CoV-2 antibody test data and prior SARS-CoV-2 test reporting from members of 9,224 Utah households. We paired these data with a probabilistic model of household importation and transmission. We calculated a maximum likelihood estimate of the importation probability, mean and variability of household transmission probability, and sensitivity and specificity of test data. Given our household transmission estimates, we estimated the threshold of non-household transmission required for epidemic growth in the population. Results We estimated that individuals in our study households had a 0.41% (95% CI 0.32%– 0.51%) chance of acquiring SARS-CoV-2 infection outside their household. Our household secondary attack rate estimate was 36% (27%– 48%), substantially higher than the crude estimate of 16% unadjusted for imperfect serological test specificity and other factors. We found evidence for high variability in individual transmissibility, with higher probability of no transmissions or many transmissions compared to standard models. With household transmission at our estimates, the average number of non-household transmissions per case must be kept below 0.41 (0.33–0.52) to avoid continued growth of the pandemic in Utah. Conclusions Our findings suggest that crude estimates of household secondary attack rate based on serology data without accounting for false positive tests may underestimate the true average transmissibility, even when test specificity is high. Our finding of potential high variability (overdispersion) in transmissibility of infected individuals is consistent with characterizing SARS-CoV-2 transmission being largely driven by superspreading from a minority of infected individuals. Mitigation efforts targeting large households and other locations where many people congregate indoors might curb continued spread of the virus.

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High variability in transmission of SARS-CoV-2 within households and implications for control

10.1101/2021.01.29.20248797 ◽

2021 ◽

Author(s):

Damon J.A. Toth ◽

Alexander B. Beams ◽

Lindsay T. Keegan ◽

Yue Zhang ◽

Tom Greene ◽

...

Keyword(s):

Test Data ◽

Attack Rate ◽

Serological Test ◽

Close Contact ◽

Antibody Test ◽

High Variability ◽

Test Accuracy ◽

Household Transmission ◽

Wide Range ◽

Test Specificity

AbstractBackgroundSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses a high risk of transmission in close-contact indoor settings, which may include households. Prior studies have found a wide range of household secondary attack rates and may contain biases due to simplifying assumptions about transmission variability and test accuracy.MethodsWe compiled serological SARS-CoV-2 antibody test data and prior PCR test reporting from members of more than 9000 Utah households. We paired these data with a probabilistic model of household importation and transmission. We calculated a maximum likelihood estimate of the importation probability, mean and variability of household transmission probability, and sensitivity and specificity of test data. Given our household transmission estimates, we estimated the threshold of non-household transmission required for epidemic growth in the population.ResultsWe estimated that individuals in our study households had a 0.38% (95% CI 0.30% – 0.48%) chance of acquiring SARS-CoV-2 infection outside their household. Our household secondary attack rate estimate was 35% (26% – 47%), substantially higher than the crude estimate of 15% unadjusted for imperfect serological test specificity and other factors. We found evidence for high variability in individual transmissibility, with higher probability of no transmissions or many transmissions compared to standard models. With household transmission at our estimates, the average number of non-household transmissions per case must be kept below 0.40 (0.32 – 0.51) to avoid continued growth of the Utah epidemic.ConclusionsOur findings suggest that crude estimates of household secondary attack rate based on serology data without accounting for false positive tests may underestimate the true average transmissibility, even when test specificity is high. Our finding of potential high variability (overdispersion) in transmissibility of infected individuals is consistent with characterizing SARS-CoV-2 transmission being largely driven by superspreading from a minority of infected individuals. Mitigation efforts targeting large households and other locations where many people congregate indoors might curb continued spread of the virus.

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Investigation of SARS-CoV-2 faecal shedding in the community: a prospective household cohort study (COVID-LIV) in the UK

BMC Infectious Diseases ◽

10.1186/s12879-021-06443-7 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Natasha Marcella Vaselli ◽

Wega Setiabudi ◽

Krishanthi Subramaniam ◽

Emily R. Adams ◽

Lance Turtle ◽

...

Keyword(s):

Cohort Study ◽

Gastrointestinal Symptoms ◽

Oral Route ◽

Observational Cohort Study ◽

Prospective Observational Cohort Study ◽

Household Transmission ◽

Community Transmission ◽

Observational Cohort ◽

The Uk ◽

Study Participants

Abstract Background SARS-CoV-2 is frequently shed in the stool of patients hospitalised with COVID-19. The extent of faecal shedding of SARS-CoV-2 among individuals in the community, and its potential to contribute to spread of disease, is unknown. Methods In this prospective, observational cohort study among households in Liverpool, UK, participants underwent weekly nasal/throat swabbing to detect SARS-CoV-2 virus, over a 12-week period from enrolment starting July 2020. Participants that tested positive for SARS-CoV-2 were asked to provide a stool sample three and 14 days later. In addition, in October and November 2020, during a period of high community transmission, stool sampling was undertaken to determine the prevalence of SARS-CoV-2 faecal shedding among all study participants. SARS-CoV-2 RNA was detected using Real-Time PCR. Results A total of 434 participants from 176 households were enrolled. Eighteen participants (4.2%: 95% confidence interval [CI] 2.5–6.5%) tested positive for SARS-CoV-2 virus on nasal/throat swabs and of these, 3/17 (18%: 95% CI 4–43%) had SARS-CoV-2 detected in stool. Two of three participants demonstrated ongoing faecal shedding of SARS-CoV-2, without gastrointestinal symptoms, after testing negative for SARS-CoV-2 in respiratory samples. Among 165/434 participants without SARS-CoV-2 infection and who took part in the prevalence study, none had SARS-CoV-2 in stool. There was no demonstrable household transmission of SARS-CoV-2 among households containing a participant with faecal shedding. Conclusions Faecal shedding of SARS-CoV-2 occurred among community participants with confirmed SARS-CoV-2 infection. However, during a period of high community transmission, faecal shedding of SARS-CoV-2 was not detected among participants without SARS-CoV-2 infection. It is unlikely that the faecal-oral route plays a significant role in household and community transmission of SARS-CoV-2.

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SARS-CoV-2 B.1.1.7 variant of concern detected in a pet dog and cat after exposure to a person with COVID-19, USA

10.21203/rs.3.rs-418665/v1 ◽

2021 ◽

Author(s):

Sarah Hamer ◽

Ria Ghai ◽

Italo B. Zecca ◽

Lisa D. Auckland ◽

Christopher M. Roundy ◽

...

Keyword(s):

Neutralizing Antibodies ◽

Nasal Swab ◽

Companion Animals ◽

The United States ◽

Genome Sequences ◽

Oral Swab ◽

Qrt Pcr ◽

Household Transmission ◽

Transmission Study

Abstract As part of a longitudinal household transmission study of pets living with persons with COVID-19 in Texas, two pets were confirmed to be infected with the SARS-CoV-2 B.1.1.7 variant of concern (VOC). The pets were a dog and a cat from the same household, sampled two days after their owner tested positive for COVID-19. The oral, nasal, and fur swabs for both pets tested positive for SARS-CoV-2 by qRT-PCR and consensus whole genome sequences from the dog and cat were 100 % identical and matched the B.1.1.7 VOC. Virus was isolated from the cat’s nasal swab. One month after initial detection of infection, the pets were re-tested twice at which time only the fur swabs (both pets) and oral swab (dog only) remained positive, and neutralizing antibodies for SARS-CoV-2 were present in both animals. Sneezing by both pets was noted by the owner in the weeks between initial and follow-up testing. This study documents the first detection of B.1.1.7. in companion animals in the United States, and the first genome recovery and isolation of B.1.1.7 variant of concern globally in any animal.

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High attack rates of SARS-CoV-2 infection through household-transmission: a prospective study

10.1101/2020.11.02.20224485 ◽

2020 ◽

Author(s):

Kanika Kuwelker ◽

Fan Zhou ◽

Bjørn Blomberg ◽

Sarah Lartey ◽

Karl Albert Brokstad ◽

...

Keyword(s):

Attack Rate ◽

Index Case ◽

Rt Pcr ◽

Younger Adults ◽

Household Transmission ◽

Antibody Titres ◽

Household Members ◽

Polymerase Chain ◽

A Prospective Study ◽

Rule Out

AbstractBackgroundHousehold attack rates of SARS-CoV-2 ranging from 7% to 38% have been reported, using reverse transcription polymerase chain reaction (RT-PCR) of respiratory samples. Lower attack rates were described in children, but the importance of age in household transmission dynamics remains to be clarified.MethodsDuring the first month of the outbreak, we enrolled 112 households (291 participants) in a prospective case-ascertained study, collecting demographic and clinical data from index cases and household members. Sera were collected 6-8 weeks after index case symptom onset, to measure SARS-CoV-2-specific antibodies.FindingsT Local Ethics Committee (#118664). he overall household attack rate was 45% assessed by seroconversion, and 47% when also including RT-PCR positives. Serology identified a significantly higher number of infected household members than RT-PCR. Attack rates were equally high in children (43%) and young adults (46%), but highest among household members aged ≥60 years (72%). The attack rate was 16% in asymptomatic household members, and 42% in RT-PCR negative household members. Older adults generally had higher antibody titres than younger adults. The risk of household transmission was higher when the index case had fever or dyspnoea during acute illness but not associated with cough.InterpretationSerological assays provide more accurate estimates of household secondary attack rate than RT-PCR, especially among children who have a lower RT-PCR positivity rate. Children are equally susceptible to infection as adults, but elderly show higher attack rates. Negative RT-PCR or lack of symptoms are not sufficient to rule out infection in household members.FundingHelse Vest (F-11628), Trond Mohn Foundation (TMS2020TMT05).

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Role of children in household transmission of COVID-19

Archives of Disease in Childhood ◽

10.1136/archdischild-2020-319910 ◽

2020 ◽

pp. archdischild-2020-319910 ◽

Cited By ~ 13

Author(s):

Jieun Kim ◽

Young June Choe ◽

Jin Lee ◽

Young Joon Park ◽

Ok Park ◽

...

Keyword(s):

Attack Rate ◽

Index Case ◽

Clinical Findings ◽

International Travel ◽

Contact Tracing ◽

Secondary Case ◽

Household Transmission ◽

Household Members ◽

Index Cases

ObjectiveTransmissibility of COVID-19 by children in the household is not clear. Herein, we describe children’s role in household transmission of COVID-19.Design and settingAll paediatric COVID-19 index cases and their household members reported from 20 January to 6 April 2020 in South Korea were reviewed. The secondary attack rate (SAR) from child index case to household secondary case was calculated. Epidemiological and clinical findings of child index case-household secondary case pair was assessed.ResultsA total of 107 paediatric COVID-19 index cases and 248 of their household members were identified. One pair of paediatric index-secondary household case was identified, giving a household SAR of 0.5% (95% CI 0.0% to 2.6%). The index case was self-quarantined at home after international travel, stayed in her room, but shared a meal table with the secondary case.ConclusionThe SAR from children to household members was low in the setting of social distancing, underscoring the importance of rigorous contact tracing and early isolation in limiting transmission within households.

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