Mitigating the return of acute respiratory virus infections

Over the past two years, many countries have seen low levels of acute respiratory virus infection (ARVIs), a collective term for all respiratory viruses that infect humans, except for SARS-CoV-2. With the cessation of non-pharmacological interventions across many countries, SARS-CoV-2 continues to circulate and the incidences of influenza, respiratory syncytial virus (RSV), and other respiratory viruses have increased this winter. For instance, Australia has recently experienced one of its most severe influenza seasons on record.1 In the US in November 2022, the Centers for Disease Control and Prevention (CDC) issued a health alert notice due to a surge in respiratory virus activity. Hospital admissions in the US related to influenza are at the highest levels in 10 years, and an early, severe spike in RSV cases resulted in considerable pressures on paediatric hospital beds.2

There are several explanations for why this has happened. Firstly, most populations had little exposure to acute respiratory virus infection other than SARS-CoV-2 over the past two years. This has caused a loss of natural immunity, predisposing them to infection. Secondly, highly transmissible SARS-CoV-2 subvariants continue to appear and infect populations, including those that have been fully vaccinated and boosted. In Europe, North America, and Africa the prevalence of omicron subvariants in the BQ.1 family is rising quickly, even when cases seem to fall overall. In Asian countries, including Singapore, Bangladesh, and India, another lineage called XBB has set off fresh waves of infection.3 Thirdly, in the absence of any policies that prevent interactions, social mixing will increase dramatically over the coming months and will increase the risk of respiratory virus co-infection. Knowledge of SARS-CoV-2 co-infection combined with other respiratory viruses is limited and seems to be associated with more severe disease.4 Finally, exposure to cold temperatures itself is often associated with increased incidence and severity of acute respiratory virus infections. Inhalation of cold air, cooling of the body surface, and cold stress resulting from lowering core body temperatures induces pathophysiological responses.56

What can we do to tackle this respiratory virus syndemic? First and foremost, vaccination with the 2022-23 influenza vaccine and covid-19 vaccine boosters for the most vulnerable populations and those people most likely to transmit should be prioritised. High levels of vaccine hesitancy exist in the UK, especially among healthcare workers, ethnic minority groups, and children, all of whom are at high risk of being infected and propagating virus to others.7891011 Targeted interventions to tackle vaccine hesitancy, especially towards parents, ethnic minority communities, and healthcare workers are required to maximise protection against infection. These should take place using multilingual, non-stigmatising, public health messaging that is available on a variety of media channels, and should address common false beliefs and misinformation around vaccines.

Secondly, the high incidence of acute respiratory virus infections in the winter period will provide additional pressure on hospital healthcare services. In the UK “ARVI hubs” established by the Department of Health and Social Care are in the early stages of development.12 If implemented correctly, such hubs could support patients with urgent clinical needs by enhancing same-day access to assessment and antiviral treatment, while reducing the substantial burden of respiratory virus infections on ambulance callouts and primary and secondary care.

Thirdly, in the absence of vaccines and antivirals for many respiratory viruses such as adenoviruses, human metapneumovirus, rhinoviruses, and the lack of uptake of influenza vaccine and covid-19 boosters, there are limited options available to mitigate the effects of acute respiratory virus infections this winter. Wearing masks in public areas and at work remains a practical and effective means of reducing transmission of respiratory viruses.1314 Increased use of filtering face piece (FFP) masks in healthcare settings will likely decrease the incidence of nosocomial virus transmission and associated sick leave of healthcare workers. The use of masks may be a major reason why influenza cases are at all-time lows in Japan, where masking is a long established practice to minimise respiratory infection, even though most northern hemisphere countries are seeing a strong resurgence of influenza.15

Finally, policy makers must recognise the importance of asymptomatic and presymptomatic respiratory virus transmission within infection prevention guidelines. In the UK, healthcare workers who have no symptoms of respiratory infection are no longer required to test for covid-19 on a regular basis.16 However, for covid-19, individuals are most infectious early in illness, before or at the start of symptom onset.17 Thus, during periods of high respiratory virus incidence, regular screening programmes using lateral flow assays for SARS-CoV-2, preferably using tests that are highly sensitive to recently circulating variants, should be implemented.18 Evidence for the efficacy and impact of healthcare worker screening using rapid antigen tests for influenza and other respiratory viruses is lacking and should be prioritised.

In summary, acute respiratory virus infections continue to emerge this winter and will likely do the same in future winters. Targeted vaccination campaigns and screening programmes will help lower transmission within the community and hospital settings while efficient setup of treatment hubs may help to reduce the burdens of these infections on hospitals. In addition, the widespread adoption of mask wearing cannot be underestimated as a simple measure to help alleviate the spread and impact of respiratory viruses this winter and should be recommended to the public by all healthcare professionals.