Researchers from Duke University, Federal University of Paraiba, University of Sao Paulo and the Oswaldo Cruz Foundation have looked at the link between the COVID-19 pandemic in Brazil and other factors, including the incidence of dengue fever in the region. Their study, entitled, “How cities with super-spread, highways, availability of hospital beds, and dengue fever affect the COVID-19 epidemic in Brazil,” released a pre-peer review on preprint. medRxiv* earlier this week.
What is this study about?
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 has gripped the world in a deadly pandemic that began late last year and, to date, has infected more than 32 million people. Brazil is third in the total number of COVID-19 cases. in more than 4.6 million. The first cases reported in the country on February 26, 2020.
Since the pandemic declaration in March 2020, international airports have been closed in the country to prevent the entry of infected people and the spread of the disease. Despite this, the geographic spread of infection was uneven across the country, write the investigators. The causes behind this uneven distribution of cases and the death rate in different parts of the country are unknown.
The researchers wrote, “… the route taken by SARS-CoV-2 to reach the rest of Brazil remains mysterious today.” The country has five official regions, “North (NO), Northeast (NE), Mid-West (CO), Southeast (SE) and South (S)”. Cases and deaths were unevenly distributed across the region, they wrote. There are differences in the incidence of new cases, the rate of growth or spread, the date of arrival of new cases from abroad, and the death rate. This was studied during the first six months of the pandemic in Brazil in this study.
Maps of Brazil are used to represent longitudinal (AD), transverse (EH), diagonal (IL), radial (MP), and connector (QT) major highway routes, as well as geographic evolution. distribution of COVID-19 cases on three dates (1 April, 1 June and 1 August), and distribution of COVID-19 deaths on 1 August (D). Overall, a cluster of 26 highways (see text) across all five road categories accounts for about 30% of the COVID-19 cases that are spreading across Brazil. The number of these multiple highways is highlighted in red. Note how many hotspots (in red) for COVID-19 cases occurred in micro-regions containing cities located along major highway routes such as BRs 101, 116, 222, 232, 236, 272, 364, 374, 381, 010, 050, 060, 450, and 465. Although the spread of COVID-19 cases and deaths are correlated, the geographical differences between the two distributions can be seen clearly by comparing them on August 1 (C and D). The color coding (See Figure below) ranks Brazil’s micro-regions (each consisting of multiple cranes) according to the number of COVID-19 cases and deaths.
What was found?
The results of this study indicate that there are four significant factors associated with the uneven spread of COVID-19 cases in Brazil. This is found using mathematical modeling. Some of the highlights of these findings are;
- The super-spreading areas include the city of São Paulo where there are 80 percent of all cases in the country
- 16 cities accounted for 98 to 99 percent of all cases in the first 3 months of the pandemic.
- The 26 major highways are responsible for 30 percent of the spread of COVID-19 cases
- Cases are increasing in rural areas. However, due to the lack of intensive care unit (ICU) beds in rural areas, the seriously ill cases had to be moved to the cities where they died of infection. This led to a mortality rate in sloping cities, write the researchers. They call it the “boomerang effect.”
- There were 3.5 million cases of dengue fever between January 2019 and July 2020. Areas with high antibody (IgM) levels for dengue fever have a lower incidence of COVID-19, as well as lower rates of infection growth and mortality. .
- The negative relationship between COVID-19 is not seen with IgM data for the Chikungunya virus
- The team wrote, “Although there are more cases of dengue fever in the NE, compared to the NO region, the region is dominated by cities with high COVID-19 and a low incidence of dengue … More cities with a high incidence of dengue fever, and a very low incidence of COVID-19, occurring in the SE and SO regions. “There is a very low incidence of cases in Paraná, Santa Catarina, Rio Grande do Sul, Mato Grosso do Sul after the initial surge in March 2020.
(A) Individual contributions from 17 state capitals responsible for 98% of the spread of COVID-19 cases for 5,570 cities in Brazil, from March 1 to June 11. Note how São Paulo contributed to more than 80% of all cases that spread during the first weeks of March. During the period until 11 June, São Paulo’s contribution never fell below 30%. For this reason, the city is labeled as the city that spreads COVID-19 in Brazil. Note also the high contributions of Rio de Janeiro, Brasilia, and the five state capitals of the Northeast: Fortaleza, Recife, Salvador, São Luís, and João Pessoa. Manaus and Belém are the largest distribution cities in the Northern region (Amazon) and Porto Alegre and Curitiba the most important in the South. During this period, the contribution of Goiânia, Campo Grande and Cuibá, to the Central-West region was the largest in their region but much smaller in comparison to other regions and their distribution. (B) Bar indicates the day the first COVID-19 case (blue bar) was officially reported in each state (using São Paulo’s first case on 26 February 2020 as a reference 0), the number of days estimated by the mathematical model for each state is 500 cases per 100,000 population (yellow bars), and the days each Brazilian state actually hit the 500 cases per 100,000 population mark (orange bars). Note how long it takes states such as MT, BA, SC, SP, GO, MS, PR, MG to reach the 500 / 100,000 mark when compared to states such as AP, AM, RR, AC, PA, and TO in the Region north, MA, CE, PB, PI, SE, AL, and RN in the Northeast region, ES in the Southeast region, and DF in the Mid-West region.
Implications of the findings
The team wrote, “This inverse correlation between COVID-19 and dengue fever was further observed in a sample of countries in Asia and Latin America, as well as on islands in the Pacific and Indian Ocean.” They note that there is a possibility of “immunological cross-reactivity” between DENV serotypes (dengue antibody) and SARS-CoV-2, dengue infection or immunization with the dengue vaccine can protect against SARS-CoV-2 so that it is safe and effective against SARS-CoV- 2 is available.
Professor Miguel Nicolelis, lead author of the study from Duke University, said in a statement that viruses could have cross-reactivity that could be explored. This is an unexpected finding from this study, he said.
The researchers speculate that there are other flaviviruses such as Zika and yellow fever that may have cross immunological interactions with SARS-CoV-2, which need to be explored. This can provide a solution to stop the growth rate of the infection. They especially hope the yellow fever vaccine can help prevent the spread of SARS-CoV-2 if it shows cross-immunoreactivity. This speculation, however, will require clinical studies to prove effective until a safe and effective vaccine against the virus becomes available.
* Important Notice
medRxiv publishes preliminary scientific reports that are not peer reviewed and, therefore, should not be construed as conclusions, guidelines for health-related clinical / behavioral practice, or are treated as defined information.
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