Chik…What? — Twenty-Seven Years Later, Are We Doing Enough?

"Chik…what?"

In 1999, I began a Cybermed article with those words.

An unfamiliar mosquito-borne illness had appeared in Port Klang. The report I cited then recorded twenty-seven people affected since December 1998. Eighty per cent were adult women. Fever, a maculopapular rash and striking migratory joint pains involving the hands, wrists, ankles and feet were prominent.

Flooding had preceded the outbreak. Aedes aegypti — already very familiar to Malaysians because of dengue — was implicated.

In collaboration with the Western Australian Centre for Pathology and Medical Research, rubella, dengue and other alphaviruses were ruled out. Six of six samples tested were IgM-positive for chikungunya. Local testing was becoming available through the WHO Collaborating Centre for Arbovirus Reference and Research in Kuala Lumpur.

Prof Lam Sai Kit and Dr Chua Kaw Bing were closely involved in investigating the outbreak. Temasek Life Sciences Laboratory now credits Dr Chua with discovering Malaysia's first chikungunya outbreak. Lam and Chua also provided Cybermed readers with an accompanying article on alphaviruses. Chikungunya was not a new virus. But to many Malaysian doctors it was certainly a new name.

I wrote then:

"One wonders, if we are doing enough to control vector-borne diseases."

Twenty-seven years later, it seems reasonable to ask the question again.

Because chikungunya did not disappear.

Chikungunya travelled

1999	2026
Virus isolation and serology described in the 1999 account	Current capabilities include RT-PCR, serology and genomic surveillance
No licensed vaccine	Vaccine options vary by jurisdiction; IXCHIQ's US approval withdrawn in January 2026; no WHO global recommendation yet
Supportive treatment	Still no specific antiviral treatment
Chronic joint symptoms recognised	Better characterised; treatment evidence remains imperfect
Mosquito control fundamental	Mosquito control still fundamental

Since the large Indian Ocean epidemics of the mid-2000s, chikungunya has spread through Asia and the Americas and has appeared in places where local transmission would once have seemed improbable.

WHO's April 2026 assessment reported 502,264 cases, including 208,335 confirmed cases, and 186 deaths from 41 countries and territories during 2025. Transmission was reported by 18 countries from January through March 2026. That assessment described chikungunya as a "significant and growing global health risk", while rating the overall global public-health risk as moderate. ^{WHO 2026}

The distinction matters. This is not a claim that chikungunya rises everywhere every year. Reporting is incomplete and transmission varies greatly by region. It means that the geographical opportunity for transmission has expanded.

Aedes aegypti remains a formidable urban vector. Aedes albopictus extends the ecological possibilities further. Urbanisation, travel, environmental change and climatic conditions favourable to mosquitoes have helped redraw the map.

Infected travellers can introduce the virus to places where suitable mosquitoes already live. Mosquito spread and the environments we create give it further opportunities.

What has medicine changed?

Quite a lot. And, in one important respect, surprisingly little.

In 1999 we relied heavily on virus isolation and serology. Today RT-PCR can identify chikungunya early in illness, while molecular epidemiology and genomic sequencing can follow transmission and viral evolution with a precision that would have seemed extraordinary then.

Our clinical thinking has also become more integrated. WHO's 2025 clinical guideline deliberately considers dengue, chikungunya, Zika and yellow fever together. Their early presentations can overlap and more than one arbovirus may circulate in the same population.

That makes sense in Malaysia. Fever and rash do not arrive carrying labels saying "dengue" or "chikungunya".

The patient's immune system matters too. CDC guidance reviewed in August 2026 highlights the risk of severe arboviral disease in immunocompromised patients, particularly those receiving B-cell-depleting treatments such as rituximab. These treatments can blunt antibody responses, making serology less reliable; diagnosis often requires molecular testing. The host belongs in our thinking alongside the virus and the mosquito. ^{CDC guidance, August 2026}

But treatment exposes the limits of our progress. There is still no specific antiviral treatment for chikungunya. Acute management remains supportive, with rest, fluids and paracetamol for fever and pain. Aspirin and other NSAIDs should be avoided until dengue has been ruled out because of the bleeding risk. ^{CDC treatment guidance}

The fever may disappear. The joint pain may not.

Prof Lam and Dr Chua emphasised severe arthralgia and arthritis in their 1999 article. They were right to do so.

For some patients, musculoskeletal symptoms persist for months or longer and can cause substantial disability. The historical article also reported chloroquine as a promising treatment for unresolved arthritis. That was the evidence landscape then. It should not be converted into a treatment recommendation today.

Management of persistent post-chikungunya musculoskeletal disease is now more nuanced. Analgesia, appropriate anti-inflammatory treatment and physical therapy may help; persistent inflammatory arthritis warrants clinical reassessment and, where necessary, specialist care. ^CDC

It is a useful reminder: promising is not the same as proven.

For most of the years that I followed chikungunya on Vads Corner, there was no licensed vaccine. That has changed.

IXCHIQ and VIMKUNYA have received regulatory approvals, but their status differs. The FDA suspended IXCHIQ's US licence in August 2025 over serious safety concerns; its accelerated approval was withdrawn on 29 January 2026. ^{FDA safety notice} ^{FDA withdrawal record}

VIMKUNYA remains FDA-approved. The UK has retained IXCHIQ with tighter restrictions. Vaccine use depends on local guidance and individual risk. ^{FDA VIMKUNYA} ^{MHRA, February 2026}

WHO has not yet issued a global recommendation for either vaccine and continues to review the evidence. ^{WHO vaccine Q&A}

So the arrival of vaccines changes the conversation. It does not end it.

The mosquito looks familiar

Aedes aegypti has not changed much since 1999. What has changed is what we know about it, what we have done about it, and — in some places — what we are now doing differently.

The same Aedes mosquitoes can transmit dengue, chikungunya and Zika. The same urban environment can support them. The same breeding container does not care which virus the mosquito eventually carries.

Why, then, should our prevention thinking begin with the disease rather than the vector and the environment?

Malaysia has been one of the countries exploring a different approach to Aedes control: Wolbachia.

In the Malaysian population-replacement approach, Aedes aegypti carrying the wAlbB strain of Wolbachia are released to establish the inherited bacterium in local mosquito populations and reduce their ability to transmit viruses.

A Malaysian operational study in high-rise residential dengue hotspots compared 20 release sites with 76 control sites. It estimated an average 62.4% reduction in dengue incidence at the observed mean Wolbachia frequency, with a 95% credible interval of 50–71%. The estimated reduction increased as Wolbachia became more common in the mosquito population. ^{Malaysian operational study}

That is important evidence from an operational comparison, not a randomised trial. It is neither a universal Malaysian effect size nor evidence of an equivalent reduction in chikungunya.

Wolbachia is better thought of as another layer of defence rather than the replacement for everything that came before it.

And that brings us to malaria.

The malaria lesson

Malaria may provide the clearest example of where vector-borne disease control is heading.

We have effective antimalarial drugs. We have insecticide-treated bed nets. We have indoor residual spraying where appropriate. We have chemoprevention. We have rapid diagnosis and surveillance. And now we have vaccines.

WHO recommends both RTS,S/AS01 and R21/Matrix-M for prevention of Plasmodium falciparum malaria in children living in endemic areas, prioritising areas of moderate and high transmission. ^{WHO malaria vaccines 2026}

R21/Matrix-M provides a second WHO-recommended vaccine option, expanding the possibilities for malaria prevention; neither vaccine replaces mosquito control, prompt treatment or other preventive measures.

In phase III trials, both vaccines reduced malaria cases by more than 50% during the first year after vaccination. WHO reports about a 75% reduction when the vaccines are given seasonally in highly seasonal settings where seasonal malaria chemoprevention is also provided.

During introduction of RTS,S to more than two million children in Ghana, Kenya and Malawi, an independent evaluation found a vaccine-attributable 13% reduction in all-cause mortality (excluding injury) among vaccine-eligible children and a substantial reduction in hospitalisation for severe malaria. ^{WHO malaria guidelines, 2025} ^{WHO malaria vaccines 2026}

This does not mean malaria has been solved. WHO estimated 282 million cases and 610,000 deaths in 2024. ^{WHO malaria figures}

But malaria teaches us something important.

The vaccine did not replace the bed net. It did not replace mosquito control. It did not replace treatment. It did not replace chemoprevention.

It added another layer.

Perhaps the lesson from malaria is not that we have finally found the answer. It is that there was never going to be one answer.

Are we still reacting too late?

When the response is mainly reactive, the sequence can look like this:

Patient → diagnosis → notification → cluster → response.

But mosquitoes respond to ecology before hospitals respond to patients.

Rainfall, temperature, water storage, construction, population movement, vector density and insecticide resistance can change transmission risk before the first patient reaches a clinic.

Epidemiological, entomological, meteorological, environmental and genomic data can increasingly be brought together to identify changing risk earlier. WHO's Global Arbovirus Initiative calls for stronger monitoring, prediction and early detection. Predictive models still need prospective validation and a response that can act on their warnings. ^{WHO Global Arbovirus Initiative}

Earlier detection also depends on making it easier for families to report illness. A 2026 study following 4,461 children in Mérida, Mexico, during 2021–2023 combined household visits, calls, SMS, a toll-free reporting line and routine surveillance. The toll-free line identified just over half of confirmed cases and had the shortest interval from symptom onset to testing. This was one paediatric cohort within a supported research programme, not proof that the same approach will work equally well everywhere. But it offers a practical lesson: accessible reporting deserves a place alongside sophisticated prediction. ^{Barrera-Fuentes et al., 2026}

The objective is simple:

Don't wait for the outbreak to tell us where the risk was.

There is a danger in becoming fascinated by sophisticated technology.

Aedes aegypti succeeds partly because we have built an environment that suits it. Water-holding containers, poorly managed waste, construction sites and drainage problems create breeding opportunities that can undermine control and call for sustained environmental action.

WHO's 2026 larval source management manual brings Anopheles and Aedes control into the same operational guidance, covering environmental modification, container and waste management, larviciding and biological control adapted to local conditions. ^{WHO operational manual, 2026}

Vector control therefore cannot belong only to the Ministry of Health. It involves local authorities, housing, construction, water management, waste management, schools, workplaces and households.

A genetically altered mosquito may be technologically impressive. A drain that does not retain water is considerably less exciting.

Both may matter.

Stop fighting one disease at a time

The mosquito does not respect the organisational chart of the health service. The drainage problem that breeds Aedes does not belong specifically to the dengue programme.

Integration does not mean treating all vector-borne diseases as biologically identical. Aedes, Anopheles and Culex have different biology; the intervention must still fit the vector, pathogen and setting.

It means allowing surveillance, laboratories, entomology, environmental intelligence, resistance monitoring and outbreak preparedness to talk to one another, with communities involved in the response. ^WHO

The better framework may therefore be:

VECTOR + PATHOGEN + HOST + ENVIRONMENT

A layered defence

I would bring these approaches together as a series of overlapping layers, selected for the local setting:

Know the threat — integrated disease and mosquito surveillance.

Anticipate the threat — environmental, meteorological and epidemiological early warning.

Reduce the vector — source reduction, appropriate insecticides, larval control and resistance monitoring.

Change the vector where evidence supports it — Wolbachia and other carefully evaluated biological approaches.

Change the environment — drainage, water storage, construction practices, waste management and urban design.

Protect the individual — repellents, screens, nets where appropriate and vaccination when indicated.

Treat disease well — rapid diagnosis, supportive treatment for arboviral disease, effective antimalarials and appropriate management of chronic chikungunya complications.

Measure what matters — not merely mosquito counts, litres of insecticide sprayed or premises inspected, but infections, hospitalisations, disability and deaths prevented.

No layer has to be perfect. The objective is to reduce transmission, prevent severe illness and limit lasting disability.

Twenty-seven years later

In 1999 I wondered whether we were doing enough.

Twenty-seven years later, we have many more ways to answer the question.

The challenge now is to use them together.

Sources & further reading

Historical sources — Vads Corner/Cybermed, 1999

Scientific and authoritative sources

The Vads Corner archive links preserve the historical record; contemporary clinical and regulatory statements above refer to the linked WHO, CDC, FDA, MHRA and peer-reviewed sources.

Published 21/2026 · 18 September 2026 · Corrections policy