Transmission of the seasonal influenza virus did not demonstrate a positive association with HIV-positive status despite the increased vulnerability to infection in individuals with HIV, according to a study recently published in the Journal of Infectious Diseases.
This case-ascertained study on household transmission of influenza was conducted in 2013 and 2014 in Klerksdorp and Pietermaritzburg, South Africa. Index cases, which included the first household case of illness resembling influenza that tested positive in real-time reverse transcription polymerase chain reaction (rRT-PCR), were recorded between May and October of each year. These tests were performed by collecting nasopharyngeal swabs and performing rRT-PCR every 4 days.
Comparisons were performed using previous findings from 2013 overall serial interval and secondary infection risk, which did not include HIV-positive status. The necessary sample size was calculated using a 40% HIV prevalence in index cases and secondary infection risk of 10% in index cases of people who were HIV negative and 20% in those who were HIV positive. Logistic regression was used to investigate factors related to secondary infection risk.
Participants in this study included 28 individuals with HIV and 57 without, all of whom were index cases, as well as 333 household contacts. HIV infection was negatively associated with household influenza transmission, with a secondary infection risk of 16% (18/113) vs 27% (59/220) for those without HIV (adjusted odds ratio [aOR] 0.2; 95% CI, 0.1-0.6). Secondary infection risk was greater in index cases with an age between 1 and 4 years (aOR 3.6; 95% CI, 1.2-11.3) and 25 and 44 years (aOR 8.0; 95% CI, 1.8-36.7). Secondary infection risk was higher in those sharing a sleeping space with index cases (aOR 2.7; 95% CI, 1.3-5.5), and was comparatively higher in contacts aged 1 to 4 years (aOR 3.5; 95% CI, 1.2-10.3) than in those aged 5 to 14 years. No association was identified between HIV-positive status and serial interval.
This study was limited by a lack of knowledge of HIV status for half of the household contacts, limiting the ability to investigate links between infection and contact HIV status. Because CD4 counts were not available, evaluation of the effects of immunosuppression on influenza transmission was also limited.
The researchers concluded that “index cases [of people with HIV] are less likely than [those without] HIV to transmit influenza virus infection to their household contacts. This suggests that even in high HIV prevalence settings, increased infectiousness of [people with] HIV [is] not an important driver of community influenza transmission.”
Researchers also noted that “children aged 1-4 years and adults aged 25-44 years are more likely to transmit influenza. These age groups could potentially be targeted by vaccination strategies aiming to reduce community transmission.”
Researchers C Cohen reports grant support from Sanofi Pasteur, Advanced Vaccine Initiative as well as travel reimbursement from Paraxel.
Cohen C, Tshangela A, Valley-Omar Z, et al. Household transmission of seasonal influenza from HIV-infected and -uninfected individuals in South Africa, 2013-2014 [published online December 12, 2018]. J Infect Dis. doi:10.1093/infdis/jiy702