United States: The COVID-19 pandemic prompted the implementation of rigorous nonpharmaceutical interventions such as lockdowns, quarantines, mask mandates, and social distancing across numerous nations to curb the transmission of the novel coronavirus. Consequently, the global prevalence of various communicable viral, bacterial, and airborne infectious diseases experienced a significant decline.
However, with the gradual relaxation of pandemic-related restrictions, a resurgence of communicable infectious diseases has been observed, particularly in affluent countries.
Upsurge in Tuberculosis, Measles, and Influenza
Despite the achievement stating that measles was eliminated in the United States in 2000, measles continued to rise and increase in the context of COVID-19 and after the pandemic. CDC started monitoring measles on 1st January 2020, and up until 28th March 2024, a total of 338 confirmed cases have been reported. Of these 338 persons, 91% had not received the vaccine, or their vaccination status was unknown. Notably, nearly one-third of these cases appeared in the first quarter of 2024, which was 17 times the level observed in the first quarters of 2020 through 2023. This resurgence has led the CDC to deem the eradication of measles in the US as being at risk.
It is worth mentioning that the overall number of TB cases has always remained comparatively low in the US compared to many countries, even historically. Still, as acknowledged, the decline in new TB cases in 2020 was followed by the gradual increase in the incidence across all age groups in 2022 and 2023 from 2.5 to 2. Rates of diagnosed NTDs were computed using the number of cases per 100,000 people.
The same pattern was identified with influenza, indicating that the same factors that contributed to increased susceptibility to the flu also resulted in increasing the odds of flu-related complications. Compared to the control group, outbreaks were nearly absent during the pandemic and returned in the winter of 2021 when COVID restrictions started to disappear. During the flu season of 2023-2024, the CDC approximated flu-related cases to be at 34 million, 380,000 flu-related hospitalizations, and 24,000 flu-related deaths in the United States.
Stuart Ray from Johns Hopkins University stated the following: On communicable diseases in the pandemic Infectious Disease Advisor As we transition to living post-pandemic, the public expects other diseases such as measles, TB, and influenza to be out of the picture.
Factors Contributing to the Resurgence
Dr. Ray explained that the behavioral synergy of social distancing, reduced travel, and masking significantly curtailed these airborne diseases. The resurgence is multifaceted, involving increased testing and surveillance, along with heightened vigilance and anxiety post-pandemic. Inadequate funding and surveillance for TB, coupled with growing drug resistance, exacerbate this issue. Despite TB rates rebounding post-pandemic, they remain below the levels observed in the 1960s.
Interruption of Routine Vaccinations
Dr. Ray noted that the Bacille Calmette-Guerin vaccine prevents severe TB forms but is ineffective against pulmonary TB. Behavioral changes rather than vaccinations contributed to the decline in TB infections during the pandemic and their subsequent rise. For measles and influenza, disrupted vaccination schedules during the pandemic played a significant role in the resurgence. Increased influenza vaccination rates during the pandemic contributed to lower infection rates, but subsequent vaccine hesitancy and a return to normal behaviors led to sustained outbreaks.
Vaccine Hesitancy and Misinformation
Dr. Ray emphasized that vaccine hesitancy, exacerbated by COVID-19 misinformation, has impacted vaccination rates for other diseases. Misunderstanding the concept of sterilizing vaccination has led to skepticism about vaccine efficacy. For measles, vaccine hesitancy intersects with xenophobia, as higher measles rates in other countries influence perceptions in the US. Herd immunity, requiring high immunity rates, is jeopardized when vaccination rates drop.
Immunity Debt Concept
Addressing the concept of “immunity debt,” Dr. Ray warned against misinterpretation. While delayed exposure to common pathogens could lead to infections later, it does not imply a debt in immune development. Some infections may be more severe if contracted later in life, but common respiratory viruses do not worsen significantly with age. The resurgence of influenza post-pandemic is attributed to increased susceptibility due to lower infection rates during the pandemic.
Strategies to Combat the Resurgence
Dr. Ray outlined strategies to control the resurgence of infectious diseases. For TB, managing drug resistance and screening is crucial. For measles, increasing vaccination rates, building trust, and developing a non-live vaccine for immunocompromised individuals are essential. For influenza, researchers aim to develop vaccines that are less dependent on variable antigens. Removing political influences from vaccination efforts is also necessary.
Lessons from the COVID-19 Pandemic
Dr. Ray highlighted several lessons from the pandemic that are applicable to other infectious diseases. Increased surveillance and behavioral strategies like social distancing and masking proved effective. Telemedicine emerged as a valuable tool, enabling patient care without exposure. Coupling telemedicine with reliable self-testing can mitigate the risk of super-spreader events. Improved ventilation and normalizing mask-wearing in public spaces can also help manage infection risk.
Measles, being a human-exclusive virus, could be eradicated with concerted efforts. TB, also primarily a human bacterium, presents a similar possibility. However, influenza, affecting various animals, poses a greater challenge for eradication.