Household transmission of rotavirus in a community with rotavirus vaccination in Quininde, Ecuador

Abstract

Background: We studied the transmission of rotavirus infection in households in peri-urban Ecuador in the vaccination era.

Methods: Stool samples were collected from household contacts of child rotavirus cases, diarrhea controls and healthy controls following presentation of the index child to health facilities. Rotavirus infection status of contacts was determined by RT-qPCR. We examined factors associated with transmissibility (index-case characteristics) and susceptibility (household-contact characteristics).

Results: Amongst cases, diarrhea controls and healthy control household contacts, infection attack rates (iAR) were 55%, 8% and 2%, (n = 137, 130, 137) respectively. iARs were higher from index cases with vomiting, and amongst siblings. Disease ARs were higher when the index child was <18 months and had vomiting, with household contact <10 years and those sharing a room with the index case being more susceptible. We found no evidence of asymptomatic infections leading to disease transmission.

Conclusion: Transmission rates of rotavirus are high in households with an infected child, while background infections are rare. We have identified factors associated with transmission (vomiting/young age of index case) and susceptibility (young age/sharing a room/being a sibling of the index case). Vaccination may lead to indirect benefits by averting episodes or reducing symptoms in vaccinees.

Figure 1. Calendar month distribution of index cases (n = 39) diarrhea controls (n = 40) and healthy controls (n = 40).

Figure 2. Infection and disease households with a rotavirus index case.

Each line represents infection and disease events in one household. Index cases are plotted in black (n = 39). Other cases of rotavirus gastroenteritis in the household are plotted in red and are plotted on the time axis in terms of time of onset relative to time of onset of the index case. Household contacts with asymptomatic infection are plotted in blue (off the time scale, since we cannot know at what time they become infected) and contacts remaining uninfected are plotted in grey. The size of the points are relative to the number of individuals with a given outcome; for reference the size of the index cases (black dots) represents a single individual.

Figure 3. Infection (grey) and disease (red) attack rates amongst household contacts of index cases for (A) case characteristics and (B) contact characteristics.

Figure 4. Distribution of cycle threshold (Ct) values in (A) case households (B) diarrhea control households and (C) healthy control households.

Black bars indicate index children (who were positive by ELISA in the case households and negative by ELISA in the control households, by definition. Red bars indicate symptomatic household contacts; grey bars indicate asymptomatic household contacts.

Figure 5. Genotype (G- and P-type) profiles of infections amongst rotavirus index cases and household contacts.

The first 2 columns represent the G and P types (respectively) of the typeable index cases (n = 35) and, with each typeable household contact (n = 57) shown to the right of the index case. Single G and P-tpye infections are color-coded; mixed infections are in black and un-typeable G- or P-types are in grey.