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Pandemic may be masking cases of arbovirus diseases, indicates seminar


27/09/2021

Cristina Azevedo (Fiocruz News Agency)

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Diseases that Brazilians are very familiar with, such as dengue fever, zika and chikungunya, are being directly affected by the pandemic, both with the transfer of human and material resources to the fight against COVID-19 and with possible undernotifications. But we can learn lessons from this experience, as shown by the 20th Advanced Seminaries on Global Health and Health Diplomacy of the Fiocruz Global Health Center (CRIS/Fiocruz), held last Thursday (September 23rd). And as indicated by the Challenges and opportunities to control arbovirus diseases in COVID-19 times webinar, this problem is not limited to Brazil or Latin America.

With the pandemic, many municipalities were forced to suspend home visits that are usually made to fight the vectors of these diseases, while others saw cases of dengue fever plummet. “Diseases caused by arboviruses are affected by many factors”, mentioned mediator Maria Gloria Teixeira, professor of Epidemiology at the Institute of Collective Health of the Federal University of Bahia (UFBA) and researcher of the Center for Data Integration and Knowledge for Health (Cidacs, in the Portuguese acronym) of the Gonçalo Moniz Institute - Fiocruz Bahia. As for urban arbovirus diseases, focusing on households is not enough, because “mosquitoes go after food”, she added.

The two sides of isolation

Although peaks of these diseases are reported every three or five years, other reasons may be behind the supposed drop in their incidence. While about two million cases of dengue fever were reported in Brazil in 2019, in 2020 there were 1.3 million cases reported. Chikungunya cases dropped from 159 thousand to 87 thousand; zika from 26 thousand to 16 thousand. “Brazil is a huge country, with a big population and a large surveillance system. But we have been seeing surveillance of arbovirus-caused diseases dropped not only in Brazil, but in other countries as well, as health workers are moved to the fight against COVID-19”, observed Marcos Espinal, director of the Department of Transmissible Diseases and Health Analysis of the Pan-American Health Organization (PAHO).

The main authority on the subject in the region, Espinal says the pandemic exposed the fragility of the health system, interrupted flights that carried provisions, and delayed public health programs. “Forty-six percent of countries interrupted essential health services in a light or moderate fashion. Latin America and the Caribbean were the most affected regions, with a rate of 49%”, he commented. A context that affected not only arbovirus diseases, but also diseases such as tuberculosis and AIDS.

On the other hand, the pandemic has created the opportunity to study the impact of social distancing on arbovirus diseases, mentioned Annelies Wilder-Smith, professor of Emerging Infectious Diseases at the London School of Hygiene and Tropical Medicine. Cases of dengue fever, for instance, have dropped in Singapore, Peru and Ecuador, but have gone up in Taiwan, Bhutan and Sri Lanka. “There is an ongoing methodological difficulty, because lockdown took place in different moments and not always coincided with the seasonality of the disease”, she highlighted. “But we have noticed that the strongest factor for this decline was the closing of schools and reduction of people’s mobility”.

New strategies and hot spots

Professor of Environmental Sciences at Emory University in the United States, Argentinian Gonzalo Vasquez Prokopec said that transmission of the disease within households could increase even with a lockdown in place. Mentioning a research in Iquitos, Peru, he said that disease transmission occurs not only at home (54% of cases) but also at nearby places (raising this rate to 66%). Taking into account how hard it is to access the inside of households, and with the limited results obtained by fumigation, it becomes necessary to innovate, design strategies, and involve the community.

“In the Mexican state of Yucatán, 80% of cases were concentrated in Mérida, where 50% of cases were in an area that corresponded to 30% of the municipality. Using this piece of information, in collaboration with PAHO, we have generated a new paradigm for the fight: working on transmission hotspots”, he said. “Based on previous information, we can improve surveillance and predict areas of higher risk.”

Agents can orient the population, for instance, providing instructions on where to apply insecticides (Aedes aegypti usually stays up to 1.5 meters above ground level), on how to choose long-lasting insecticides that are quick to apply. Nets in windows and doors can reduce zika cases by more than 60%. “COVID is not going to disappear. We need to increment resources and strategies, and we also need to involve the community”, he stated.

Drones against breeding grounds

Involving community leaders was one of the bets placed by the city of Belo Horizonte, says Fabiano Pimenta, subsecretary of Health Promotion and Surveillance of the city. With the pandemic, people began being afraid of letting agents into their homes. One of the solutions was to donate masks to locals. Agents began working more intensely with the areas around the households and avoided accessing the homes of inhabitants who belonged to risk groups. Even then, in 2020 visits dropped by one million when compared with the previous year.

Drones were used to locate possible breeding grounds for vectors and to apply herbicides where agents could not get in. “The training of personnel is a one-way road only, it is crucial if Brazil and Latin America want to reduce arbovirus-related diseases”, he says.

The seminar was also attended by researcher Sérgio Luz, of the Leônidas and Maria Deane Institute (ILMD/Fiocruz Amazônia), as a debater. Sérgio was the one who first came up with the idea of the seminar, says Paulo Buss, Cris/Fiocruz coordinator.

Seminars and Journals

The Advanced Seminars in Health Diplomacy are one of the products of Cris/Fiocruz and are also part of its function as an observatory. In addition to helping the Fiocruz presidency in international agreements, Cris/Fiocruz also publishes, every 15 days, its Information Journals on Global Health and Health Diplomacy with analysis on the subject, divided by geographical areas.

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