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- Published: September 12, 2019
- https://doi.org/10.1371/journal.pntd.0007575
Chikungunya is caused by an arbovirus RNA of the genus alphavirus (CHIKV) of Togaviridae family [1]. Symptomatic acute CHIKV infection is mainly characterized by high fever and severe joint pain (arthralgia) that can compromise daily life activities [2]. Acute symptoms (such as fever, myalgia, and exanthema) usually resolve or decrease in intensity (arthralgias) in 1 or 2 weeks, although the acute phase may last up to 21 days [1, 3]. Clinical features of post-acute phase, which begins after 3 weeks of onset of symptoms and may extend for 90 days, include polyarthralgia, polyarthritis, exacerbation of comorbidities, chronic fatigue, and worsening of preexisting degenerative or traumatic arthropathies [1, 3]. The persistence of arthralgia for more than 3 months indicates the transition to the chronic stage of chikungunya. In addition to joint pain, exacerbation of comorbidities, tenosynovitis, tendinitis, and neuritis have been reported in patients in the chronic phase of the disease [2–4]. Before the epidemic in the Indian Ocean islands (the Comoros, Mauritius, the Seychelles, Madagascar, Mayotte, and Reunion) and in India between 2005 and 2006, there were no consistent reports of severe cases or chikungunya-related deaths [5, 6]. Particularly, the chikungunya outbreak in Reunion Island revealed unknown characteristics of the disease, such as arthralgia persisting for more than 15 months (with critical implications in quality of life) and high lethality among elderly patients with preexisting conditions, such as hypertension and diabetes [5, 7]. Corroborating these findings, more than 4,500 excess deaths were estimated to have occurred in Ahmedabad, India [8], and Mauritius [9] during the 2005–2006 chikungunya epidemics.
These findings were published at least 4 years before the virus hit the island of Saint Martin in September 2013. Yet the American and Caribbean preparedness and response to the introduction of CHIKV was precarious; as of 2017, only Canada, Cuba, and Chile did not observe autochthonous cases in the region, and the Pan American Health Organization (PAHO) reported 631 chikungunya deaths among 2.5 million cases [10]. This number of deaths, however, is largely underestimated. Considering only 3 states of northeastern Brazil (Pernambuco, Rio Grande do Norte e Bahia) and 4 countries/territories in the Americas (Dominican Republic, Puerto Rico, Guadeloupe, and Martinique), an excess mortality of more than 14,000 deaths during chikungunya epidemics has been estimated for the years 2014 to 2016, mainly concentrated among the elderly [11–14]. There is no comprehensive estimate of excess mortality for Colombia and Brazil (after 2016), the countries that recorded the largest CHIKV epidemics, along with the Dominican Republic. Nonetheless, if a similar excess mortality pattern is considered, more than 35,000 deaths caused primarily or secondarily by CHIKV infection may have occurred in the Americas and the Caribbean in about 4 years (2014–2017).
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Currently, CHIKV transmission in the Americas is very low. Yet it is expected that new outbreaks will emerge as the virus spreads to new areas (in the Americas and other regions) and as the susceptible population in previously affected areas builds up. In anticipation of new epidemics, it is critical that new protocols of chikungunya management be devised, with a particular attention to mortality prevention, especially among well-known high-risk groups. Failure to do so will result, once again, in an unacceptable number of chikungunya-related deaths. While most of these deaths may not get reported, as recently happened, all will be foretold. Time will tell.