Impact of coronavirus disease 2019 (COVID-19) pandemic isolation measures on the rate of non–COVID-19 infections in hematology patients

Laws concerning social distancing and restrictions on public life have been implemented globally during the COVID-19 pandemic. In turn, hospitals have changed their practice, from reduced visitation hours to stronger emphasis on hand hygiene. It would not be surprising, therefore, if transmission of non–COVID-19 infections were to decrease during this time, and data have started to emerge to support reduced incidence. ¹

In this study, we aimed to assess whether the incidence of non–COVID-19 infections had changed in a population of hematology patients while they have been subject to changes in infection control practices during the COVID-19 pandemic (Appendix 1 online). The hematology patient cohort was selected for the study population because they are often more susceptible to infections (from underlying disease or treatment), which, in turn, can result in higher rates of morbidity and mortality. ² The outcomes of this study will be used to inform continuation of isolation and infection control measures as the pandemic continues to evolve and afterward.

Methods

Monash Health is a large, tertiary-care health network in southeastern Australia with a 32-bed hematology inpatient service. Hematology inpatients admitted between January 24 and May 23 (inclusive) for 2019 and 2020 were included in the study, a 4-month period from when the first patient with COVID-19 in Australia was admitted to Monash Health (January 24, 2020) and the equivalent dates the year prior to minimize effects of seasonal variation. Typical presentations for hospital admission included febrile neutropenia and elective inpatient chemotherapy.

All respiratory pathogen polymerase chain reaction (PCR), fecal pathogen PCR, and blood culture results from the cohorts were collated, and the proportion and breakdown of positive results were analyzed. Multiplex PCR assays (AusDiagnostics, Mascot, Australia) included targets for pathogens (Appendix 2 online). The rates of infection for each year were compared using the χ ² test or the Fisher exact as required. Statistical significance was set at P < .05. Statistical analyses were performed using Stata version 12.1 software (StataCorp LP, College Station, TX).

Any organism identified more than once in an individual patient within 7 days was considered a duplicate result. Regarding blood cultures, some organisms (listed in Appendix 2 online) were defined as contaminants if they were isolated in a single culture, but they were defined as pathogens if they were isolated in >1 culture within 7 days in the same patient.

Results

Overall, 1,598 patients were admitted in the 2019 date range and 1,488 were admitted in 2020. The difference in infection rates was statistically significant for respiratory PCR (20.27% vs 10.90%; P = .01) but not for fecal PCR (8.00% vs 6.76%; P = 1.00) or blood cultures (3.27% vs 3.41%; P = .88) (Table 1).

Table 1. Breakdown of Microbiology Results by Type

Note. PCR, polymerase chain reaction.

^a Includes cultures in which >1 organism was isolated.

Respiratory PCR virus swabs were procured in patients with respiratory infective symptoms and/or fever, and asymptomatic patients were not routinely tested. In 2019, 22 of the swabs were taken in the first 48 hours of presentation, and 24 were taken in 2020. The incidence of respiratory virus infection was lower in 2020 with 29 of 143 (20.27%) positive tests in 2019 compared to 29 of 266 (10.90%) in 2020 (P = .01). No cases of COVID-19 were identified. The incidence of all respiratory viruses was lower in 2020 except for respiratory syncytial virus and rhinovirus/enterovirus (Table 1).

There was no significant difference in the incidence of fecal pathogens, with 6 of 75 positive tests (8.00%) in 2019 compared to 5 of 74 (6.76%) in 2020 (P = .77). The rates of positive blood cultures were similar, with 27 of 826 positive isolates (3.27%) in 2019 compared with 28 of 822 (3.41%) in 2020, P = .88. Gram-negative bacilli were isolated in 19 positive blood cultures in both years. Excluding skin flora isolates, gram-positive organisms were isolated in 8 blood cultures in 2019 and 7 in 2020.

Discussion

The percentage of positive respiratory PCR results was significantly lower in 2020 than 2019, when the hospital implemented changes in infection control practices and visitor restrictions during the COVID-19 pandemic (Appendix 1 online). The notable increase in the rates of rhinovirus/enterovirus in 2020, however, may be due to reduced activity of alcohol-based hand sanitizers on nonenveloped viruses. ³

Blood cultures and fecal PCR results did not show statistically different rates of infection; these were mostly commensals or infections less affected by droplet precaution measures implemented during the pandemic.

Although similar numbers of blood cultures and fecal PCR samples were taken each year, we attribute the increased number of respiratory PCR samples taken in 2020 to heightened awareness for testing during the pandemic. Greater than 75% of all positive respiratory PCR samples were taken within 48 hours of admission, and although the results are unlikely to solely reflect community exposure (ie, our hematology patients frequently attend day treatment centers and other hospital services), a limitation is the difficulty in accounting for the expected reduction of circulating non–COVID-19 respiratory viruses in the community due to government restrictions and public behavior.

In hematology patients, viral infections are an important cause of morbidity and mortality. ^4,5 Therefore, increased awareness and utilization of infection control measures is vital for reducing rates of infection. Although our study was retrospective, we found a reduced rate of viral respiratory infection when stricter measures were in place at our hospital. This is a useful indication of their effectiveness, and incorporation into general hematology infection control can be considered. Further studies are warranted to assess the extent and duration of the impacts resulting from increased use of hand-sanitizer, limiting ward visitation, and social distancing on reducing infections within the hematology patient population.