Research exhibits the influence of COVID-19 restrictions on dengue circumstances in 2020

Almost three quarters of 1,000,000 fewer world circumstances of dengue occurred in 2020, which could possibly be linked to COVID-19 disruptions limiting human mobility and call, based on a brand new research revealed in Lancet Infectious Illnesses.

Researchers from the London College of Hygiene & Tropical Medication (LSHTM), Beijing Regular College and different worldwide companions, funded by the Medical Analysis Council, analyzed the month-to-month dengue circumstances from the World Well being Group (WHO) Weekly studies between 2014 to 2020 from 23 international locations – 16 in Latin America and 7 in South East Asia, the primary areas the place dengue is endemic, in addition to local weather information on air temperature, relative humidity and precipitation.

They discovered a powerful affiliation between faculty closures and declines in non-residential journeys, similar to buying or utilizing public transport, on account of COVID-19 and diminished threat of dengue transmission. This means that locations similar to faculties and generally visited public areas could possibly be dengue transmission sizzling spots and play a key position in spreading the illness.

Additional analysis is required into how human motion behaviors (the locations individuals go to, how lengthy they spend there and with whom) influence dengue transmission threat. This might assist resolution makers determine if measures like contact tracing, testing or quarantine might assist management the unfold of the illness.

At present dengue management efforts are centered on or across the households of people that get sick. We now know that, in some international locations, we also needs to be focusing measures on the places they lately visited to cut back dengue transmission. For all of the hurt it has prompted, this pandemic has given us a possibility to tell new interventions and concentrating on methods to forestall dengue.”.

Dr Oliver Brady, Affiliate Professor and MRC Fellow at LSHTM and research senior writer

Dengue is a viral an infection transmitted by the Aedes species of mosquitoes, which causes flu-like signs. It’s present in tropical and sub-tropical climates worldwide, and is commonest in city areas.

It is without doubt one of the solely infectious illnesses to point out a sustained enhance in circumstances every year, and the WHO now estimates that round half the world’s inhabitants is susceptible to contracting dengue.

Transmission is carefully linked to the climate, surrounding surroundings and human mobility. It is usually carefully related to the local weather, with sizzling and humid tropical climates very best for transmission. Dengue season in lots of international locations happens round June to September, when peaks in circumstances may cause overcrowding in hospitals – very like with COVID-19.

Dengue is simply unfold from mosquito to human and vice versa, and isn’t transmitted from people to different people. Nonetheless, adjustments in individuals’s actions and conduct could impact transmission, for instance by way of diminished publicity to mosquitoes or fewer alternatives for contaminated individuals to exit and about and move on the virus to uninfected mosquitoes current there. COVID-19 and the restrictions on human motion that had been imposed in the course of the pandemic due to this fact present a singular alternative to discover how human motion and conduct contribute to dengue transmission.

Dengue case numbers abruptly started to say no in April 2020 in lots of international locations, following the introduction of public well being and social measures concentrating on the unfold of COVID-19 and the ensuing change in human motion and shift to extra time spent in residential locations. In 2020, dengue circumstances decreased by 40.2% in Latin America and 58.4% in South East Asia, with simply over two million circumstances recorded within the Americas and South East Asia in 2020.

Nonetheless, unraveling the impacts of COVID-19 disruption is advanced as 2019 noticed the biggest world dengue outbreak in historical past, with greater than 5.2 million circumstances recorded within the Americas and South East Asia area. This led to excessive ranges of immunity which might even be anticipated to cut back dengue circumstances in 2020.

Dr Brady added: “Earlier than this research, we did not know whether or not COVID-19 disruption might enhance or lower the worldwide burden of dengue. Whereas we might assume discount in human motion would scale back the virus transmission, it could additionally disrupt the mosquito management measures already in place. This disruption could end in long-term impacts on dengue circumstances which could not be evident till the following epidemic.”

The analysis workforce checked out two totally different measures of COVID-19 associated disruption – public well being and social measures, similar to faculty and public transport closure, stay-at-home necessities, gathering restrictions; and human motion conduct by way of time spent at residential and public places. Additionally they accounted for the totally different strengths of restrictions in lockdowns in several international locations all over the world.

By combining all this information and analyzing traits, they had been capable of present that diminished time spent in public areas was carefully related to diminished dengue threat.

9 out of 11 international locations in Central America, the Caribbean and the Philippines noticed a whole suppression of their 2020 dengue season, with different international locations experiencing a a lot diminished season. In international locations the place the COVID-19 restriction measures started on the peak of dengue season, there was a sharper than anticipated decline in circumstances, regardless of above common incidence being recorded earlier within the yr.

This lower in circumstances is also attributed to diminished charges in individuals searching for therapy, the next potential for misdiagnosis and diminished availability for laboratory testing for dengue might end in misdiagnosis. Nonetheless, some international locations similar to Sri Lanka predicted this could possibly be an issue in the beginning of the pandemic, so undertook outreach work to encourage individuals to get identified and search therapy. Regardless of this, there was no change in charges of extreme circumstances and deaths reported, suggesting the discount in therapy searching for was not the trigger for the discount in circumstances.

A greater understanding of how treatment-seeking behaviors change throughout an epidemic is required, as entry to care and speedy diagnostics change with a view to absolutely assess and interpret the change in case numbers.  The workforce emphasizes the necessity for long term, extra routine measurement of the prevalence of dengue inside every inhabitants.

Though general circumstances declined in 2020, Peru and Singapore reported worse than common dengue incidence in 2020. This might have occurred as a result of unpredictable pure year-to-year variation in dengue incidence that happens on account of, for instance, the emergence of various dengue virus variants, or might trace on the higher position being bitten by mosquitoes at residence performs in spreading dengue in these international locations.

Because the local weather recorded in 2020 was just like the common local weather of the final six years, the researchers didn’t discover an affiliation between local weather and the discount in dengue threat throughout 2020.

The researchers observe that it stays to be seen how lots of the estimated 0.72 million circumstances had been actually averted, or simply delayed till later years as human motion returns to pre-COVID ranges and say it is key to proceed monitoring dengue traits in 2022 and past.

The researchers acknowledge the constraints of this research, together with lack of information on the several types of dengue, which may drive outbreaks, and the potential adjustments in dengue reporting ensuing from COVID-19 disruptions.


London College of Hygiene & Tropical Medication (LSHTM)

Journal reference:

Chen, Y., et al. (2022) Measuring the results of COVID-19-related disruption on dengue transmission in southeast Asia and Latin America: a statistical modelling research. The Lancet Infectious Illnesses.

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