To the Editor:
Chikungunya virus (CHIKV) is an enveloped, spherical single-stranded RNA virus about 60–70 nm in diameter, belonging to the alphavirus genus and family Togaviridae. CHIKV is transmitted by Aedes species mosquito vectors and causes an acute disabling illness characterized by high fever and severe arthralgia called chikungunya fever (CHIKF)1,2. The word chikungunya means “the one which bends up” in the Makonde dialect of Tanzania; it refers to severe joint pain characteristic of acute disease2. CHIKV was isolated in Tanzania in 1952 during a dengue-like outbreak1,2,3. Since then, CHIKV has caused outbreaks in Africa, Asia, the Indian Ocean region, and Europe, with severe medical and economic effects1. In December 2013, CHIKV was reported in the Americas on the island of Saint Martin. Since then, more than 2.9 million cases have been reported in 45 countries in North, Central, and South America3.
The history of CHIKF in the Americas is probably at least 200 years old4. For centuries, CHIKV existed in forested regions of eastern Africa in an enzootic life cycle that affected arboreal mosquito vectors and nonhuman primates5. Phylogenetic analysis suggests that there has been periodic emergence of an epidemic life cycle; this includes the spreading beyond Africa to the new world in ships containing infected individuals, Aedes mosquitoes, and stagnant water6.
Brazil is a tropical and subtropical country of 210 million people. It is infested in every state with Aedes mosquitoes. Major outbreaks in Brazil of dengue and Zika virus infection have been widely reported. They result from the tropical environment, urban crowding, and challenges in vector control. The first locally transmitted CHIKV infection in Brazil occurred in September 2014 in the state of Amapá (North), followed by an outbreak in the state of Bahia (Northeast). In the same year, 1425 autochthonous cases of CHIKF were confirmed by clinical-epidemiological and/or laboratory criteria. By the end of 2015, 38,332 suspected autochthonous CHIKF cases were reported and of these, 13,236 were confirmed, with 6 deaths. In 2016, there were 263,598 suspected CHIKF cases in 2700 cities and 145,059 confirmed cases, which resulted in more than 200 deaths. As of September 2017, 171,930 suspected cases and 121,734 confirmed cases were reported7,8 (Table 1).
As of September 2017, among the 5 Brazilian federal regions, the Northeast had the highest number of reported cases and confirmed deaths, with > 400,000 cases and 278 deaths9. Ceará, in the Northeast, reported > 149,760 probable CHIKF cases. In addition, the epidemic is spreading toward the Southeast and North regions (Figure 1).
Of the 3 CHIKV genotypes, the Asian one, reported in the Caribbean, was detected in the state of Amapá, and the East/Central/South African (ECSA) genotype, which had not previously been detected in the Americas, was confirmed in the state of Bahia. Brazil therefore harbors the highest diversity of CHIKV in the Americas10.
In Brazil and throughout the Americas, CHIKF significantly affects rheumatology practice. Following acute CHIKF, up to 60% of patients develop arthralgia, arthritis, myalgia, and fatigue, lasting up to 3 years1. Physicians in endemic areas are confronted with large numbers of patients with chronic disabling arthritis. The most severely affected individuals are likely to be referred to rheumatologists. There is a lack of consensus about how these patients should be treated, and many drugs, including nonsteroidal antiinflammatory drugs, glucocorticoids, disease-modifying antirheumatic drugs (methotrexate, hydroxychloroquine, sulfasalazine), and biological drugs have been used to treat CHIKF chronic arthritis with limited success or evidenced-based support1,2. There is scientific interest in CHIKV vaccine development, but commercialization seems unlikely in the near future.
CHIKF is an emerging viral infection. Chronic chikungunya arthritis is an emerging rheumatic disease. The vectors of CHIKF (Aedes albopictus and Aedes aegypti) are found on every continent except Antarctica2. The Brazilian chikungunya epidemic, like previous epidemics in Africa, India, and elsewhere, has created widespread chronic rheumatic disability that is likely to recur in new epidemics in the near future. Brazil has just over 2000 rheumatologists, a limited number to manage nearly half a million reported chikungunya arthritis cases in the past 3 years9. In Brazil, studies on the effect of the disease, its characteristics, and treatment are needed. Rheumatologists in Brazil are on the front line now and need new resources to combat this infectious arthritis. It is incumbent on the entire rheumatology community to take up this challenge.
No ethics approval is required according to the authors’ institutions (Faculty of Medicine Estácio of Juazeiro do Norte, and Yale University School of Medicine). No individual human subjects were studied or exposed to any risk.