- by Gary Finnegan

Zika outbreaks must be tackled in tandem with dengue

As well as causing thousands of serious birth defects, Zika outbreaks threaten to distract us from other public health crises

The Zika virus is spread by the Aedes aegypti mosquito – a bug that is also responsible for spreading dengue fever, yellow fever, and chikungunya. The attention given to Zika is an opportunity to shine a spotlight on the major challenges posed by other vector-borne diseases, and to develop tools that can help us overcome them as a group.

Zika outbreaks have been linked to serious neurological conditions such as microcephaly and Guillain-Barré syndrome and sparked global concern. The symptoms of the disease itself are usually mild but the sudden surge in cases – coupled with distressing images of babies born with smaller than normal heads – have triggered a strong reaction.

The WHO declared a public health emergency in February 2016 in the wake of a significant rise in cases of microcephaly. The White House sought $1.9 in emergency funding to ‘prevent, detect and respond’ to the threat posed by the virus.

Then a degree of panic set in. The outbreak continued to make headlines around the world, athletes began withdrawing from the Rio Olympics due to infection fears, and cases were reported across Latin America and in the US.

With the Ebola epidemic under control, Zika has taken on the role the world’s most feared virus. The worry stems from its novelty, apparently rapid spread, and a visceral reaction to images of birth defects.

All of this is entirely understandable. Similar phenomena have been seen with SARS, H1N1, and Ebola. But what about the major public health challenges that continue in the background?

Infographic comparing the interest vs incidence for zika, dengue, malaria and yellow fever in recent years.

Interest vs incidence: Zika, dengue, malaria, yellow fever

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Permanent emergency

There were 214 million malaria cases last year, which normally kills around 30,000 people per year but the figure may be higher this year due to outbreaks in Angola and the Democratic Republic of Congo.

Dengue fever is of particular interest given its geographic spread, public health impact and capacity for disrupting health systems. It causes fever, headache, vomiting, joint pain and a skin rash, and has been linked to pregnancy risks. Spread by the same mosquito responsible for the Zika outbreak, it is the fastest-growing mosquito-borne viral infection in the world today.

In the 1970s, fewer than 10 countries reported severe dengue epidemics. Today, dengue is present in over 150 countries.

The rise in cases numbers may not be quite as dramatic as Zika, but take a step back and the growth in cases is steady and steep.

Around 40% of the world’s population live in countries where dengue is a daily risk. There are between 50 million and 400 million infections per year. A study of 10 countries in Latin America and South East Asia shows the disease is responsible for 10% of all fever episodes.

Like Zika, many cases are mild or not recorded, but it is estimated that around half a million hospitalizations result from dengue infections annually. The disease causes an estimated 20,000 deaths per annum. The economic toll of dengue fever and its impact on health systems are enormous. The total annual cost of dengue has been put at $8 billion. Hospital care of non-fatal cases accounts for half of this.

The burden of dengue on families in Latin America, Asia, and Africa can also be profound. The emotional and economic cost of losing a family member is devastating. Even non-fatal cases that require hospital treatment can cost $70 in countries where this can be the weekly income.

Add to this the lost productivity associated with missing work or education for several days or weeks and the costs quickly mount.

Dengue outbreaks have indirect effects on other health service users. Health system capacity can adapt to meet a predictable demand for malaria or diabetes care. But dengue outbreaks are sporadic, unpredictable and highly disruptive.

In this respect, the disease can be likened to the Ebola epidemic which put enormous and unexpected pressure on clinics, health workers, and laboratory infrastructure. The true public health value of controlling dengue would have system-wide positive effects.

So what can be done to stop ZIka and other vector-borne diseases?

To start with, most cases of dengue and Zika infection are not diagnosed today. Better diagnostics and disease surveillance data are required to get a handle on the true scale of the challenge – and to measure the real-world impact of preventative measures such as vector control and immunization.

To tackle this, our team at Break Dengue has launched an innovative initiative that turns big data into actionable information. ‘Dengue Track’ is a crowdsourced disease surveillance tool. Through a user-friendly online chat system, we are mapping dengue cases worldwide and giving the public free access to toolkits that help reduce their risk of infection.

By pairing this information with official data sources, a more comprehensive picture of real-time dengue outbreaks can be built. This will provide authorities and non-governmental organizations with a valuable resource on which they can make informed decisions.

In parallel, vector control, vaccination, rapid diagnostics and effective treatment for severe cases can combine to turn the tide against dengue. Zika is a serious public health challenge about which much can be learned by studying other vector-borne illnesses. By tracking the epidemiology of all of these diseases, it is clear that there is a real risk that Zika will reach regions where mosquito control has failed.

We should not view it as straight competition between dengue, chikungunya, yellow fever and Zika. There are, in fact, huge synergies in the global effort to tackle these arboviruses and other vector-borne diseases. Innovation mosquito control measures could help to curb the number of vectors while research on new treatments for one disease may turn up leads in the fight against the other.

Our Dengue Track tool can be used to map Zika – or malaria, yellow fever, chikungunya and others – just as we are doing for dengue fever.

Investment and attention are required to harness the power of the tools we have – and develop new ones – in an integrated approach to breaking dengue and other vector-borne diseases. We can do this if we do it together.

Click below to report dengue outbreaks near you using Dengue Track