By rightly garnering worldwide attention today, the Covid-19 pandemic linked to the new SARS-CoV-2 virus is eclipsing other infectious diseases. However, this situation is all the more alarming because by diverting the attention of managers, decision-makers and the public from these diseases, it can worsen their impact.
In many countries – in Africa, Asia and Latin America – the Covid-19 pandemic could thus undermine campaigns to fight and prevent tuberculosis, AIDS and malaria (main targets of the Global Fund), as well as’vaccination campaigns against diphtheria, polio and measles.
Viral diseases transmitted by mosquitoes Aedes – like dengue, Zika, chikungunya and yellow fever – are also concerned.
The situation is all the more worrying as their incidence has increased dramatically over the past decade, and that they are responsible for the serious epidemics currently affecting theLatin America, l’South East Asia and theIndian Ocean.
Serial dengue epidemics
Latin America is experiencing one of the largest dengue epidemics ever recorded in the region this year. Brazil, badly affected by the epidemic of Covid-19, has for example identified more than a million cases and around 400 deaths attributed to dengue fever between January and June 2020. The departments of Mayotte and some Guyana – who still face a significant circulation of SARS-CoV-2 – are also in a worrying situation.
More broadly, the French overseas territories are experiencing significant dengue epidemics, with more than 30,000 cases reported in Indian Ocean islands since 2017 (Mayotte and The meeting) and over 15,000 cases in the Caribbean Islands (Guadeloupe, Saint-Martin, Saint-Barthélemy and Martinique) since the end of 2019.
Temperate regions of the northern hemisphere (United States and Europe), particularly affected by the Covid-19 pandemic, are also at risk for these arboviroses during the summer, in areas where mosquito vectors Aedes aegypti and or Aedes albopictus are established. An indigenous transmission of dengue, for example, was detected this summer in France, in the department of Hérault. In the United States, around 20 cases have been identified in Florida.
In this context, in April 2020, the French Ministry of Health approached the National Agency for Food, Environmental and Occupational Health Safety (ANSES) to assess on the one hand the potential impact of the pandemic of Covid-19 and containment on surveillance and the fight against dengue, and on the other hand the benefit / risk balance of stopping or continuing certain vector control actions. This evaluation work was the subject of a report available in 3 languages (French, English and Spanish) on the ANSES website, of which we present a short summary here.
Covid-19 and dengue at the same time
The simultaneous circulation of Covid-19 and dengue can lead to a delay in diagnosis, and therefore impact the care and measures specific to each of these two diseases.
The two infections sharing some clinical features (fever, fatigue, headaches…), a differential diagnosis is necessary. In addition, the demonstration of serological results of dengue false positives in people with Covid-19 is of concern. Everything must be done to avoid errors in the diagnosis or interpretation of the tests, with dramatic consequences for both patients and public health interventions (for example, contact tracing and screening for Covid-19, and control of insect vectors for dengue).
These co-infections are naturally to be feared only in countries where the two viruses circulate. For now, Guyana has declared the death of a teenager with Covid-19 and yellow fever. Co-infection with the dengue virus and SARS-CoV-2 has so far only been documented sporadically, particularly in Thailand, at Singapore and to The meeting. It can nevertheless be feared in the countries most affected by dengue, in South East Asia et en South America.
This co-circulation of viruses increases health risks. And in countries like Brazil, where health services are still disrupted or even overwhelmed by the Covid-19 pandemic, the coexistence of the two diseases aggravates the situation. Not to mention that several dengue serotypes can circulate at the same time, as is the case in Guyana or in the meeting, hence the possibility of secondary or even tertiary infections and therefore serious clinical cases.
Impacts on dengue fever surveillance
The epidemiological surveillance of dengue is also affected by the mobilization around Covid-19. It has been observed in all the French overseas territories, where a drop in dengue cases notified and declared just after the start of containment has been described, even though the number of cases had clearly increased in previous weeks.
This underreporting of dengue cases, especially for cases which, without clinical signs of seriousness, contribute significantly to the transmission of the virus, is explained not only by the confinement and the difficulties of movement, but also by the public concern about the risk of being infected with Covid-19 in health establishments, or even by the closure of certain dispensaries and access to diagnosis made difficult.
Come back for treatment!
Mosquito control and Covid-19 guidelines
Last alarming finding: vector control interventions, and particularly those concerning the species Aedes, have been significantly affected by the mobilization of attention on Covid-19. For exemple, during containment, these interventions were reduced in the USA and in all French overseas territories.
In fact, many interventions against mosquitoes are a priori opposed to the guidelines for the prevention and control of Covid-19, sometimes requiring close contact between the agents in charge of them and the population: this is the case. especially during awareness campaigns or insecticide spraying in homes. However, in the absence of vaccines and treatments, the prevention and control of dengue and other viral diseases transmitted by Aedes rest widely on the control of vector mosquito populations, through sustainable, synergistic and proactive vector control – its effectiveness may be reduced lack of proper and integrated implementation.
Under these conditions, it is crucial to strengthen communication around the importance and the need for vector control interventions: to do this we must rely on the Internet and social networks, by jointly disseminating information on Covid-19 and on the prevention of viral diseases transmitted by mosquitoes (for example, the elimination of their breeding places by staying at home). Finally, it is necessary to adapt the existing directives for the agents in charge of vector control, in particular through barrier gestures and physical distancing, to prevent any transmission of Covid-19.
The negative impact of the Covid-19-induced crisis on dengue surveillance and control is evident in tropical areas affected by dengue. As for temperate regions, travel restrictions theoretically limit the possibilities of importing arboviruses. The risk is nevertheless present, as evidenced by fourteen dengue cases observed in France during confinement, notwithstanding the very low number of thefts from affected areas.
The resumption of air transport, even if it is partial, could increase this risk in the regions of Europe or Aedes albopictus is installed. Between the 1is May and August 21, 2020, Public health France recorded 155 imported cases of dengue and 4 imported cases of chikungunya.
It should be noted in passing that the simultaneous circulation of these diseases necessarily has deleterious effects on the economic and social plans. Social inequalities linked to dengue and other arboviruses, such as Zika, have already been highlighted. We also know that the Covid-19 pandemic exacerbates these inequalities, as we have seen in Reunion Island or United States.
In such a context, we must underline the importance of social mobilization and of maintaining or even strengthening the integrated management of diseases transmitted by mosquitoes. And we also recommend improving practices to minimize exposure to SARS-CoV-2 in vector control.
All over the world, and particularly in the intertropical zone, the threat posed by diseases that can transmit mosquitoes – such as dengue, chikungunya, Zika virus disease and yellow fever – could be accentuated due to deterioration of mosquito surveillance and control. However, this risk is likely to worsen the situation due to the Covid-19 pandemic alone.
In short, there is therefore an urgent need for public health actors and political decision-makers to develop proactive policies and to allocate adequate resources to prevent and manage the spread of these diseases in times of health crisis. All the more so since in the decades to come, we fear that other new diseases with high epidemic and pandemic potential will emerge …
The assessment was carried out by the “Group of collective expertise in the emergency on the impact of the Covid-19 pandemic and containment on dengue surveillance and vector control interventions” of the ANSES. This group was chaired by Thierry BALDET (CIRAD), coordinated by Johanna FITE (ANSES) and Elsa QUILLERY (ANSES), and it was composed of James DEVILLERS (CTIS), Marie-Marie OLIVE (IRD), Marie-Claire PATY ( Public health France), Christophe PAUPY (IRD), Philippe QUENEL (EHESP), Jocelyn RAUDE (EHESP), David ROIZ (IRD), Jean ‑ Paul STAHL (CHU Grenoble Alpes), Marie THIANN-BO-MOREL (University of La Réunion ), all those people who contributed to the writing of this article.