In the trading parlance that our stock-market-hooked city prefers, chikungunya emerged as the highest gainer in the major pests’ sector in 2024. From a two-digit annual incidence for most of the 18-odd years since it re-emerged on India’s disease surveillance map, cases of the viral fever have shot up exponentially. In 2022, the civic public health department reported 18, which increased to 250 in 2024, while this year’s tally so far is 735.
The caseload in Mumbai this year is second only to Nagpur (1,088) among Indian cities. Due to the tally in Maharashtra alone, the state has the ignominious distinction of being the chikungunya hub of the country this year.
Maharashtra’s public health department had 5,757 notifications in 2024 while Karnataka was a distant second with 2,213. The highest tally could be the result of a better reporting system in Maharashtra, but going by what hospitals and clinics indicate, chikungunya has indeed been a frequently recurring problem this year. “It swooped in this year, with cases sharply rising since September,” said Dr Hemant Thacker from Jaslok Hospital, Peddar Road.
Cases of the other mosquito-borne diseases—dengue fever and malaria—are higher in comparison and associated with complications, but it is the sudden surge associated with chikungunya this year that has made everyone notice this fever characterised by immobilising joint pain. A subset of chikungunya patients suffer from joint pain (called CHIKV arthritis) for months after getting well.
Dr Gautam Bhansali from Bombay Hospital near New Marine Lines admitted many patients of chikungunya this year because their fever was very high for days and they couldn’t get off the bed; some even needed ICU stays. Infectious diseases specialist Dr Vasant Nagvekar admitted a few in H N Reliance Hospital in Girgaum with neurological complications (encephalitis).
While it is supposed to mimic mild flu in children, paediatricians and neonatologists reported newborns with darkened skin patches and liver inflammation. Paediatrician Dr Indu Khosla had an eight-month-old admitted at SRCC Hospital, Haji Ali, who “cried incessantly”, most possibly due to pain. While darkened spots and inflamed liver or heart muscle are known symptoms of chikungunya, they are rare. Cases of mother-to-child transmission of the viral fever were also noted.
“Previously, we would see an odd patient of chikungunya needing hospitalisation and that patient was likely to be an out-of-Mumbai resident, but not anymore,” said infectious diseases specialist Dr Anita Mathew from Fortis Hospital. Sion Hospital’s head of medicine department, Dr Nitin Karnik, had previously noted that there is now local transmission of the virus.
Covid-causing coronavirus has heightened fears, especially of viruses; immediately after the pandemic ended, parts of Mumbai witnessed an outbreak of the measles virus and a few children died. “Viruses cause multi-systemic infections with involvement of multiple parts such as the throat, chest, and liver all getting affected. Bacteria, on the other hand, begin with a localised infection,” said Dr Mathew to explain why viruses are a major public health scare. Moreover, the medical responses to viral outbreaks are often not exhaustive: as Dr Thacker pointed out, the best test for chikungunya is a PCR test on the eighth day, but many doctors advise a rapid test within the first week of the infection, and that almost always shows up as a negative result.
Ever since chikungunya re-emerged in India roughly two decades back, outbreaks and epidemics have been reported from regions such as Pune and Kerala, but Mumbai has always seemed insulated from it. Not anymore though. Dr Jacob John from the community medicine department of CMC Vellore said chikungunya usually follows an eight-to-10-year pattern, with major outbreaks or epidemics reported at those intervals. “This could be because of changes in the vector (carrier) or the microbe,” he said. The Maharashtra health officials have started a genomic study on the chikungunya virus in circulation in the state.
The reason for the sudden outbreak in Mumbai could be the result of some changes in people’s immunity levels or a mismatch between the antibodies (in people) and the virus strain in circulation, said doctors. The medical lesson of 2024 for Mumbaikars could be to not consider chikungunya a simple fever-and-pain disease—and begin by ensuring that fresh water—in which the chikungunya-virus-transmitting Aedes aegypti mosquitoes breed—doesn’t collect around you (even in balcony’s corners, flower pots, or empty coconut kernels).