Global surge in infectious diseases as over 40 countries report outbreaks 10-fold over pre-pandemic levels

New analysis by Airfinity and Bloomberg News reveals outbreaks of diseases such as measles, whooping cough, tuberculosis and polio, as well as dengue and cholera are surging worldwide. 

Today’s study has compiled data from over 60 organisations and public health agencies showing that the world is seeing a resurgence of at least 13 infectious diseases, with cases higher than before the pandemic in many regions. 

Over 40 countries or territories have reported at least one infectious disease resurgence that’s 10-fold or more over their pre-pandemic baseline.

The data is presented in an interactive spike map, shown above. It shows outbreaks by disease with the spikes representing the fold change in reported cases between a post-pandemic year (2022-onwards) with highest reported incidence against a single pre-pandemic ‘baseline’ year within the 2017-2019 period, preceding the COVID-19 pandemic.

Spike map above showing fold changes in reported cases pre- and post-pandemic: all diseases

Our analysis reveals today’s outbreaks can be attributed to three main factors. The first is falling vaccination rates. Measles, polio, whooping cough (also known as pertussis) and tuberculosis are all vaccine-preventable. Declining uptake is leaving populations vulnerable and allowing the pathogens to spread. For example, global measles vaccination coverage has declined, with 20 countries in Europe falling below 90% in 2022, including the UK (87%), which is currently experiencing a national outbreak. Austria is seeing its worst measles outbreak on record as cases in the first five months of 2024 are already 190% higher than the pre-pandemic peak. Countries like Denmark, Bosnia and Herzegovina, Canada, Ireland, Netherlands are on track to surpass pre-pandemic levels if sustained transmission persists.

There is some evidence that the current pertussis outbreaks could in part be driven by pressure on the virus to gain adaptations that may impact the effectiveness of current vaccines, or that this could be occurring due to genetic drift. With a 134% post-pandemic increase in cases in 2024, Spain is among the growing number of countries in Europe to see a rising whooping cough burden. France, Norway, and the UK are also expected to surpass pre-pandemic levels soon.

The second is an overall decline in population immunity during the pandemic years. Restrictions on social interactions suppressed the circulation of pathogens such as influenza, respiratory syncytial virus (RSV), Mycoplasma pneumoniae and invasive Group A Streptococcus, known as iGAS. Today’s resurgence can be attributed largely to more susceptible populations as well as increased testing and reporting of cases following the pandemic. For example, total influenza cases in the US last season were 28% higher than in 2019. In Europe, total influenza cases last season were 75% higher than in 2019.

Spike map above showing fold changes in reported cases pre- and post-pandemic: flu, RSV, chickenpox and iGAS

The third factor is climate change which is enabling the spread of diseases such as dengue and cholera, and increasing the pathogens reach into new territories. Argentina has seen the largest rise with a 151-fold increase in dengue cases from 3,220 in 2019 to 488,035 so far this year.

As mosquitos move northward, we have seen more cases in southern Europe. Italy has seen a significant increase with its first locally acquired case detected in 2020 to 67 cases in 2023. In France, there were 65 reported cases, up from 9 in 2019, a 7.2-fold increase.

Airfinity’s Biorisk analyst Kristan Piroeva says, “Unvaccinated children are at the greatest risk from the resurgence of diseases like measles, whooping cough, polio and RSV. These illnesses can often be more severe for infants and young children than the general adult population. Ensuring sufficient vaccination rates is crucial to preventing these vulnerable groups from becoming seriously ill.

“Cases of dengue, which most people think of as a tropical disease, are growing in non-endemic countries. As temperatures continue to rise, we could see the disease becoming endemic in southern Europe. Airfinity’s global overview of dengue incidence shows nearly half the world’s population may now be at risk of dengue infection.

“An increase in surveillance and testing for disease also plays a significant role in today’s analysis. By enhancing our monitoring capabilities, we can better track the spread of these diseases and implement timely interventions to mitigate their impact.”

For more information please contact: press@airfinity.com.

*includes wild poliovirus type 1, vaccine-derived poliovirus types 1,2 and 3

** Invasive Group A Streptococcus

***Mycoplasma pneumoniae

Methodology

Airfinity has collaborated with Bloomberg News to map the post-pandemic resurgence of 13 select epidemic-prone infectious diseases. The spike size is determined by the change in reported cases from a post-pandemic year (2022-onwards), as of 1st June 2024, with highest reported incidence against a single pre-pandemic ‘baseline’ year within the 2017-2019 period, preceding the COVID-19 pandemic. The ‘baseline’ year for pertussis may be set to an earlier date, contingent on the timing of the most recent epidemic in the specific country pre-pandemic.

The diseases included in this analysis are chickenpox, cholera, dengue, measles, Mycoplasma pneumoniae, parvovirus B19, invasive Group A Streptococcus, pertussis, influenza, respiratory syncytial virus (RSV), wild poliovirus type 1 (WPV1), vaccine-derived poliovirus and tuberculosis. 

The analysis relies heavily on data reported by all countries globally, which in turn depends on the robustness of their infectious disease surveillance and reporting systems. Consequently, the data by no means represents the true burden of these diseases within populations, as many cases might go undetected due to asymptomatic presentations and mild clinical symptoms, leading to undiagnosed cases, as well as limited resources for testing. Furthermore, the disease data presented here is not exhaustive, with large gaps for both notifiable and non-notifiable diseases. Some countries/regions might be overrepresented than others due to their superior surveillance and reporting systems. In addition, changes in testing levels post-pandemic likely affect recent disease incidence, resulting in large post-pandemic spikes that might incorrectly imply significantly higher disease incidence.

Although still incomplete, 2024 data is included in the analysis. This inclusion is based on the observation that certain diseases have exhibited an already higher number of cases in the first months of 2024 than in any other year since the pandemic subsided, sometimes exceeding pre-pandemic levels. In such instances, the fold change is calculated based on year-to-date cases for 2024, with the expectation that these figures will rise as more months’ data becomes available.