News Numbers of zika cases in Rio de Janeiro have dropped sharply in recent weeks and will fall to almost nothing during the dry winter months of the Olympic and Paralympic Games, Rio 2016 organisers and medical authorities said on Tuesday (7 June) "Zika numbers started declining rapidly in April," Rio 2016 chief medical officer João Grangeiro told journalists at a press conference in Rio de Janeiro "The cooler and drier weather will reduce mosquito populations, lowering the risk of mosquito-borne infections " The zika virus circulates in almost 60 countries around the world It is transmitted by the aedes aegypti mosquito, which also carries the virus that causes dengue fever   Citing the results of computer modelling published by the Cambridge University Press in April, Games organisers estimated that only one or two tourists would contract zika during the Rio 2016 Olympic Games, which start on 5 August Zika cases in Rio de Janeiro from 1 January 2016 to 31 May 2016 (Source: Bulletin of the Secretary of State for Health) No cases of zika were reported in the 44 test events for the Olympic and Paralympic Games, in which about 7,000 athletes, 8,000 volunteers and 2,000 staff participated The test event programme began in August 2014 and was completed in May this year Many of the events took place in Rio's wetter summer months, when mosquitoes are more prevalent According to official data from the secretary of state for the health, in recent years cases of dengue in Rio have tended to peak in the rainy months of March and April and then fall to almost zero from July to September The weather in the winter months in Rio is cooler and dryer, with average temperatures of about 21 degrees celsius in August  The incidence of zika, which is carried by the same mosquito, is following the same trend Zika cases are also falling and are expected to continue to fall in the five Brazilian cities outside Rio that will host Olympic football matches Authorities said they are not relying only on dry winter weather to reduce the incidence of zika The same preventative measures will be implemented at Olympic venues and infrastructure as in the rainy months Each venue already undergoes daily inspections to make sure there are no pools of stagnant water where the mosquito tends to breed At larger sites and in the Olympic Village, these checks are carried out several times per day Organisers will brief all athletes, tourists and officials on how to protect themselves from the mosquito before they come to Rio and on arrival "Our mission is to make sure that all athletes find Rio de Janeiro to be a safe city for competing and celebrating," Rio 2016 executive communications director Mario Andrada told journalists Advice for travellers According to the World Health Organisation, there is no public health justification for postponing or cancelling the Games Brazil is one of almost 60 countries which are reporting zika cases People continue to travel between these countries for a variety of reasons, the Geneva-based WHO noted The WHO is advising athletes and visitors to Rio de Janeiro, and other areas where the zika virus is circulating, to protect themselves from mosquito bites by using insect repellents and by wearing clothing – preferably light-coloured – that covers as much of the body as possible   Because the virus can be sexually transmitted, visitors should practise safer sex or abstain from sex during their stay and for at least eight weeks after their return  Pregnant women are advised not to travel to areas with ongoing zika virus transmission, including Rio de Janeiro