What's the risk for athletes and spectators travelling to Rio this summer?
The risk of someone attending the Olympics and contracting the Zika virus is close to zero. About half a million people are expected to travel to Rio this summer: a study from this week estimates that between 3 and 37 of these people will catch Zika (0.00006 per cent–0.000074 per cent).
In comparison, over the course of a year there are 200 million trips between the USA and countries where Zika is being actively transmitted.
Could someone who catches Zika in Rio cause an outbreak when they get back home?
Zika is spread by infected mosquitoes. The species of mosquito that carries the virus – called Aedes aegypti – doesn't exist in the UK, so there's no risk of an outbreak there. A very small number of isolated sexually transmitted cases have been reported, although this form of transmission is rare and can be mitigated by using condoms.
For other countries, we need to look at the risk proportionally. Air travel between Zika-affected countries and the rest of the world is happening every minute of every day, and travel for the Olympics represents about 0.25 per cent of it. The Olympics' contribution to the risk of international spread is a drop in the ocean.
What's the risk for pregnant women?
Pregnant women, or women who are planning to get pregnant, have been advised to avoid travelling to the Games. This is because Zika can cause developmental problems and small heads (microcephaly) in a small proportion of babies if a women gets the virus during pregnancy. The risk is thought to be especially high if infection is during the first three months of pregnancy.
Men who are planning to start a family are also advised to use condoms while travelling in a Zika-affected country, and for eight weeks after they get back (six months if they’ve had Zika symptoms).
What are officials in Rio doing to tackle the problem?
The Rio Olympics is taking place in the Brazilian winter. As a result there will be fewer mosquitos and they will also be less active than they are in the summer months.
Organisers in Rio are taking measures to reduce the risk further, such as spraying insecticides, using larvicides to kill eggs in water and running clean-up campaigns to remove the stagnant water that mosquitoes like to breed in.
How can people protect themselves?
Exposed skin should be covered at all times with a good quality repellent containing DEET or PMD, picaridin or IR3535. It’s a good idea for people to always keep 100ml bottles of repellent with them, as many of the stadiums will be operating airport-style security.
Long sleeves and loose clothing, preferably treated with permethrin, are also good for preventing bites. Aedes mosquitoes bite during the day, not just at night, so people should try to stay protected at all times by keeping doors and windows closed.
It's important to remember that for most people Zika is a very mild illness – most people won’t even realise they’ve had it. In rare cases patients can have serious complications, such as Guillain-Barré Syndrome.
How can research help?
There is still a lot we don’t understand about the Zika virus and its effects, and we need much more research that is joined up at an international level.
The race is on to find a vaccine, which could protect the people living in countries where Zika is present. However, we still don’t know how the immune system responds to the virus and how long protection lasts after infection. It will be very difficult to make a vaccine until we understand these fundamentals.
There's also important work to be done in understanding the epidemiology – how the virus affects people at a population level. We need to figure out how long it will take for the epidemic to burn itself out once a large number of people have been infected, and where the virus might crop up next.
Finally, we need a better understanding of how Zika causes microcephaly so that women can be offered the right support and advice when planning a family.
Can we stop something like this happening again?
Zika is the latest example of a virus that has seemingly come from nowhere to cause devastation – like Ebola before it. We might never be able to prevent these outbreaks, but we must get better at responding quickly once the alarm is raised.
Preparation is crucial. We need a better global governance system to allow us to be ready to respond when an outbreak hits, and reforming the World Health Organization is central to this.
We also need to be ‘research ready’ before emergencies arise so that globally coordinated action can begin as soon as possible. Wellcome, governments, business, philanthropy and civil society all have a part to play in making our world more resilient to global health threats.