In a groundbreaking study, researchers from the São José do Rio Preto Medical School in São Paulo State, Brazil, have shed light on the cryptic circulation of chikungunya virus, which can precede massive epidemics with severe public health consequences. The study, published in the journal PLOS Neglected Tropical Diseases, monitored 341 residents of Vila Toninho, a neighborhood in São José do Rio Preto, over a four-year period from 2015 to 2019.
Led by Professor Maurício Lacerda Nogueira, the research team discovered that the number of chikungunya cases in the city was initially small but gradually increased during the study period. This silent circulation of the virus highlights the need for enhanced epidemiological surveillance, genomics, and mosquito monitoring to effectively predict and prevent future epidemics.
Despite the low number of officially confirmed cases in São José do Rio Preto, which has a population of approximately 470,000, the FAMERP study revealed a significant rise in chikungunya seroprevalence, from 0.35% in 2015 to 2.3% in 2019. Additionally, analysis of blood samples collected from individuals with suspected dengue during the 2019 outbreak in the city showed that 4.4% had the virus or had recently been infected, while 8.6% had been exposed to the antigen at some point.
Professor Nogueira emphasized that the new circulation profile identified in the study does not diminish the potential threat posed by chikungunya to public health. The chronic phase of the disease, characterized by severe joint pain, can be highly incapacitating and persist for years. Furthermore, the risk of future epidemics remains high, although the study suggests that they can be more predictable with proper surveillance measures in place.
The researchers attributed the underreporting of chikungunya cases to the high rate of asymptomatic infections and the similarity of symptoms with dengue in the acute phase. Joint pain caused by chikungunya can range from mild arthralgia to debilitating polyarthritis, affecting four or more joints in the body.
Chikungunya virus was introduced to the Americas in 2013, causing major epidemics in several Central American and Caribbean countries. In Brazil, the virus was first detected in 2014 in the states of Amapá and Bahia, and it has since spread widely, with all states currently reporting its transmission.
Professor Nogueira cautioned against assuming that epidemics will manifest uniformly across different countries. Brazil's large size and the concurrent circulation of several arboviruses make epidemic trends more complex and challenging to analyze. This underscores the importance of robust disease surveillance to effectively monitor and respond to potential outbreaks.
The findings of the FAMERP study serve as a wake-up call for public health authorities and researchers alike. By investing in epidemiological surveillance, genomics, and mosquito monitoring, it is possible to predict and prevent chikungunya epidemics, mitigating their impact on public health and people's lives. The study's results reinforce the need for continued research and vigilance to combat this debilitating viral disease effectively.
