Ebola; Zika. Both diseases that were unknown to
many until recently. But there have been huge
outbreaks of both - and each time scientists and
global health experts were caught off guard.

In this week's Scrubbing Up, Dr Seth Berkley,
CEO of the Gavi, the Vaccine Alliance suggests
Ebola and Zika may be followed by other public
health emergencies fuelled by other lesser-
known diseases.

First it was Ebola and now Zika; two official
World Health Organization (WHO) Public Health
Emergencies of International Concern within as
many years.

Both diseases have been known about for
decades, and yet in both cases no vaccines or
drugs were available when we most needed
them. So what's going on?

Is this just a terrible coincidence, being caught
off-guard like this twice in such quick
succession, or is it part of a worrying trend and
a taste of things to come?

At first glance it wouldn't appear that the two
diseases have much in common. One is difficult
to catch but a ferocious killer, while the other
spreads with ease but is relatively harmless to
the vast majority of people infected.

Yet, in both cases there is something novel,
either in the way the virus has spread or in how
it affected people which has made the outbreaks
more of a threat.

In global health security terms that is a real
concern, because such sudden changes of
modus operandi can not only make public health
threats even more difficult to predict or
anticipate than normal, but also make all the
difference between a localised outbreak and
global pandemic.

Even more worrying is the fact that with
changing trends in human and animal migration,
increasing urbanisation, the density of mega
cities, the rise in antimicrobial resistance and
climate change, such threats could become
increasingly more common.

In the case of Ebola, what changed was its
ability to spread.

Historically Ebola's aggression has been its own
worst enemy; the virus often immobilising and
killing its hosts before they had the opportunity
to infect others, limiting its spread mainly to
contact with the deceased.

Because of this, for decades it remained a
relatively low impact disease, confined to small
outbreaks in remote and relatively unpopulated
rural regions.

What changed in West Africa was that for the
first time it was able to reach more densely
populated urban areas, increasing its ability to
spread almost exponentially.

With Zika it was different. It had been believed
to be a relatively benign disease, producing only
mild flu-like symptoms - if any at all.

Because of this there was little concern about
the spread of this mosquito-borne disease as it
crossed continents.

But now with a Zika outbreak suspected as the
most likely cause of a sudden spike in cases of
microcephaly in Brazil - which can cause babies
to be born with abnormally small heads - we
have another global health emergency on our
hands, particularly if reports of sexual
transmission prove valid and its spread is not
limited to mosquitoes.

If Zika is a factor with microcephaly, it is not
entirely clear why. In the seven decades since
Zika was first discovered, such horrific
complications have never before been observed.

A form of nerve damage, called Guillain-Barré
syndrome, has been seen a small number of
people, and in the case of pregnancies there
were 17 cases of malformations of the central
nervous system in foetuses following an outbreak
in French Polynesia in 2014.

However, even then Zika was not implicated until
recently, and only after the alarm was sounded
in Brazil.

So, why now? It could simply be something we
only see as a result of scale - 1.5m cases of
Zika in Brazil, compared to just 30,000 in the
worst previous outbreak.

Or it could just be that surveillance in Brazil was
good enough to detect it, picking up both
increases of Zika and microcephaly immediately,
compared to West Africa where poor health
systems meant it took three months before
Ebola was first confirmed.

Or it could be that the virus has mutated to a
more virulent strain.

Regardless, the fact remains that it could take
years before we establish a conclusive link with
microcephaly, and possibly even longer before
we understand the epidemiological factors
leading to its sudden emergence now.

What is clear is that in addition to mosquito
control in affected countries what may also be
needed is another new vaccine.

But unlike Ebola, we don't have several
candidate vaccines lined up, waiting in the wings
which we can rapidly steer through clinical trials.

Thanks to Ebola, industry has now been faster to
react and commit to develop a vaccine or adapt
existing ones, but it will still likely be years
before one is ready.

However, why does it take a global health
emergency for us to even realise no vaccine
exists in the first place?

Part of the problem is that for some serious
diseases there is simply no profit in prevention,
which means that if we want to avoid epidemics
we cannot expect industry to provide the
solution.

Instead governments, public funders and private
donors need to share the costs, and they need
to do so now, rather than waiting until the next
epidemic.

The good news is that we now already have an
idea of where to focus our attention. In
December the WHO brought together scientists
and clinicians who came up with an "initial list"
which reads like a most-wanted of the worst
eight diseases, including Ebola and other
hemorrhagic fevers like Marburg and Lassa
fever.

They also flagged a sub-set of three other
serious diseases that also needed urgent
attention, which included Zika.

And therein lies the point. None of the diseases
on the list were particularly surprising.

They are known threats, it's just that they are
not big enough threats to have warranted the
world to rally round and put in place the
incentives to develop vaccines, at least not yet.
What Zika and Ebola have both taught us is that
we can't assume pathogens will continue to
behave the same way.

We need to stop waiting until we see evidence
of a disease becoming a global threat before we
treat it like one.


www.bbc.com/news/health-35614569?ocid=socialflow_facebook

God save us