Hospital-acquired infections (HAIs) have been a growing cause for concern for many years, with methicillin-resistant staphylococcus aureus (MRSA) frequently grabbing the headlines due to its ability to cause life-threatening infections in patients. A growing body of data has shown that one of these infections – hospital-acquired pneumonia – which affects 1% of hospitalised patients in the UK, is the most common healthcare-associated infection contributing to death.

Great strides forward have been made in combatting the spread of infections in the healthcare setting, but a 2021 study by the US Centers for Disease Control and Prevention (CDC) showed that US hospitals witnessed a significant increase in HAIs in 2020, inextricably linked with the Covid-19 pandemic.

The rise of more contagious variants, notably Omicron, is part of the reason for the spike in HAIs. But equally significant is the strain that high numbers of Covid-related hospital admissions are having on staff and resources.

In 2020, research by Sameer Kadri, an intensive-care physician at the National Institutes of Health Clinical Center, showed even in the early stages of the pandemic, the risk of a Covid-19 patient dying was greater when hospital staff were strained by high caseloads. In short, surges in the number of Covid-19 cases, and consequently hospitalisations, correlated with more deaths.

Though it is less likely to result in hospitalisation, the Omicron variant is more contagious than Delta, which itself is more transmissible than other strains, making the risk of spreading it within the confines of a hospital far greater should a patient be admitted. It is due to this increase in transmission risk that Covid-19 added another reason to why overcrowding in hospitals can lead to excess deaths.

“The CDC has received reports from partners about increases in healthcare-onset SARS-CoV-2 infection, suggesting that transmission in healthcare settings has increased in some areas and facilities during the Omicron wave,” says Dr David Kuhar, who leads the hospital infection prevention team at the CDC. “As community transmission levels have been a strong predictor of transmission in healthcare settings, it is not unexpected that transmission in healthcare settings increased during the unprecedented levels of transmission seen with the spread of the Omicron variant.”

A snapshot of the situation in the UK, using figures from NHS England, shows 2,158 new positive tests in hospitals in England on 3 January 2021. Of those, only 1,635 were infections occurring “in the community”, leaving 523 cases (24%) most likely contracted in hospital – double the proportion recorded at the start of December 2020, when hospital-acquired cases accounted for only 10% of new cases.

“It is conceivable that healthcare settings may make more avid use of strategies such as source control and universal personal protective equipment during periods of increased risk, particularly respiratory virus season.”

Dr David Kuhar

“Definitely, Omicron has complicated infection control,” says B. Aditya Prakash, associate professor in the school of computational science and engineering at the Georgia Institute of Technology. “On one hand, large urban hospitals have been slammed in the ER due to the increase in Covid-19 patients, making them overcrowded, leading to greater chances for infections to spread more easily from hospital staff and patients.

“Also due to increased load, adherence to usual hygiene and preventative practices might be under stress, again leading to easier spread,” he adds. “HAIs also weaken the natural immunity of a body, serving to increase adverse effects from Covid-19. At the same time, more widespread use of PPEs and other measures introduced for Covid-19 in hospitals can have beneficial side effects for other infections too, and we are seeing some tentative evidence for that in more rural hospitals. I think it is still unclear which dynamic is the main one right now.”

Guidance and compliance

Infection prevention and control procedures to target the transmission of infection through skin contact, surfaces and airborne virus particles in healthcare settings, such as the CDC’s general infection control guidance, are well established and understood. For example, appropriate air handling, use of source control, and respirator use can reduce the risk of transmission of airborne virus particles. Regular environmental cleaning can reduce risks from surfaces, and interventions like personal protective equipment such as gowns and gloves, and hand hygiene can reduce the risk of skin contamination.

New variants, however, require incremental changes to account for increased transmissibility. The CDC, for example, updated its guidance in response to the Omicron variant in December and then again in February to include measures for mitigating staff shortages and to establish processes for dealing with exposed and infected healthcare personnel.

“Overall, the infection prevention and control recommendations for healthcare settings have not drastically changed, but have expanded in some areas, such as situations in which a respirator may be used by healthcare personnel,” remarks Kuhar.

“In healthcare settings, a number of additional infection prevention and control practices have been introduced during the pandemic to help prevent the spread of SARS-CoV-2, such as immunisation of healthcare personnel and patients or residents, the use of source control or masking by everyone in a facility, and implementing measures to reduce close contact between persons in healthcare settings, such as limiting the numbers of persons in healthcare personnel breakrooms, and limiting resident or patient group activities.”

More interventions are also being implemented, but it is adherence to these guidelines that is important to best prevent the transmission of infections in healthcare. Compliance is key.

“Adherence sometimes takes a backseat to other more pressing matters,” says Prakash, who is leading a team of multidisciplinary scientists exploring ways to use data and mathematical modelling to detect, understand, and control future HAI spread. “But by and large, limiting the spread of Covid-19 inside the hospital is crucial and hospitals have taken steps for that.”

Rising numbers of HAIs during the Covid-19 pandemic are to be expected, and they mask the fact that measures have achieved some level of success in combatting other infections.

“Efforts to reduce many hospital-acquired infections, such as catheter-associated urinary tract infections, central line-associated bloodstream infections, and C. difficile infections, have been successful overall in years prior to the pandemic,” notes Kuhar. “Reasons for decreases in hospital-acquired infections can be different for each individual healthcare-associated infection.

“Unfortunately, many healthcare-associated infection rates have increased during the pandemic, potentially due to healthcare system stresses, novel patient care processes for those with Covid-19, such as proning patients on ventilators and risking disrupting the dressing on a central line catheter, as well as modifications to typical infection prevention activities, such as central line catheter maintenance activities.”

Flattening the curve

When under such great pressure, can hospitals do more to reverse the rising trend of HAIs?

“Hospitals are doing an incredibly tough job,” says Prakash. But one thing he believes they can do better is helping healthcare workers maintain their regular hygiene regimen. This can take the form of automated systems, which can measure hygiene performance and also provide ‘nudges’ to them in case they forget important activities like handwashing.

“Another [improvement could be] using a wider spectrum of tools from infectious disease epidemiology, such as increased testing of both healthcare workers and visitors, which can quickly pick up imported cases too,” he says.

Other useful practices suggested by Prakash are “better data modelling and analysis”, in order to implement more targeted measures to detect outbreaks earlier, possibly even among asymptomatic patients, and “genomic surveillance” to monitor trends in circulating variants within healthcare settings.

For Prakash, efforts have been reasonably successful so far, though the effectiveness of preventative measures varies between healthcare institutions. He does, however, see room for improvement in using more optimised and systematic measures like data modelling.

“With increasing stress from novel pathogens, this is becoming more important,” he remarks. “In general, many hospitals have begun understanding the role of data and models and how they can be used to inform hospital management, including improving workflows. There are also HAI penalties for hospitals for readmission and other things in US law. Hence there are multiple clear incentives for hospitals to do better.”

What remains to be seen is whether the precautions introduced for Covid-19 will remain in place when the pandemic is over. It is hard to identify what has individually had the greatest impact. Perhaps effectiveness is down to compliance with all robust infection prevention and control practices, throughout any healthcare facility.

“It is difficult to say which additional infection control practices that were enacted during the pandemic in healthcare settings will be maintained after the pandemic has ended,” says Kuhar. “It is conceivable that healthcare settings may make more avid use of strategies such as source control and universal personal protective equipment during periods of increased risk, particularly respiratory virus season.

“In general, many hospitals have begun understanding the role of data and models and how they can be used to inform hospital management, including improving workflows.”

B. Aditya Prakash

“Processes have definitely been refined, although maybe we should aim for being more nimble in future,” says Prakash. “I think better surveillance and testing of visitors, patients and healthcare workers is here to stay. It is extremely clear now that all hospitals know having a strong infection prevention and control programme is necessary. Understanding the impact of different measures is broadly also an open question and an active area of research, but I believe more passive automated systems, data analysis and mathematical modelling can play an important role in determining these lessons.”

There are lessons to be learned, so the onus is on the healthcare sector to continue its in-depth analysis, even after the pandemic has passed.