Dengue Fever, Chikungunya & Zika - Advice for Crew

Over the past few years, several viral illnesses have become prevalent in South America, the Caribbean and increasingly in North America. The main illnesses are Dengue Fever, Chikungunya and more recently Zika. The common factor is the Aedes aegypti mosquito. 

Dr Spike Brggs of Medical Support Offshore (MSOS) provides an update on the risks, symptoms and management of these viral illnesses for yachts visiting or transiting affected regions:

We are used to covering up at night to avoid being bitten by the Anopheles mosquito which spreads malaria but, the problem with Aedes aegypti is that it is active at night, but mostly active during the day, increasing the chances of being bitten by an infected mosquito and contracting one of these viral illnesses.

Currrently the most important and only defence is to avoid being bitten, and the gold standard deterent is the insect repellent DEET (Diethyl-meta-toluamide). There are numerous brands on the market containing various levels of DEET, so there is a wide choice available. 

It is not always obvious when someone has contracted one of these diseases. Each illness has a spectrum of symptoms which overlap with other viral illnesses, and can sometimes be confused with flu-like symptoms. Blood tests can be performed for evidence of infection in the blood, but these need to be performed in a clinic or a hospital and are not totally reliable. 

All three illnesses are typically self-limiting in the majority of cases, and treatment involves the management of symptoms such as fever, arthralgia (joint pain) and myalgia (muscle pain), using paracetamol (acetaminophen), and maintaining hydration. 

However, all three viral illnesses can be associated with serious short- and longer-term complications.

Aedes aegypti mosquito

A brief profile of each illness is outlined below: 

Dengue Fever

Also known as ‘Breakbone Fever’ due to the incidence of severe joint and muscle pain, this is a viral illness with no specific cure, although a vaccine is available. It is spread by mosquitos active during the day (Aedes aegypti and other species) and areas affected include the Tropics and Sub-tropics, including South America, Caribbean, North America and now southern Europe. A vaccine was introduced in Mexico in December 2015 and further vaccines are in development by the WHO.

Symptoms usually appear 3-14 days after the infecting bite:

• Fever

• Arthralgia, myalgia

• Headache

• Occasional nausea and vomiting

• Rash (generalised over most of the body)

• Seek medical help, but treatment is usually just supportive (hydration and paracetamol)

• Serious complications are unusual, less than 5% of sufferers, but may include haemorrhagic fever
  
  

Chikungunya

A viral illness with no specific cure and spread by mosquitos active during the day (Aedes aegypti) as for Dengue Fever,. Affected areas include the Tropics and Sub-tropics, Caribbean, Central Americas, parts of North America, Europe and the Far East.

Symptoms usually appear 3 - 7 days after the infecting bite:

• Fever

• Arthralgia, myalgia

• Headache

• Occasional nausea and vomiting

• Rash (generalised)

• Seek medical advice, but treatment is usually just supportive (hydration and paracetamol)

• Serious complications are unusual, but joint pain can be prolonged, possibly leading to a chronic pain syndrome in rare cases, sometimes lasting years.
  
  

 Zika

A viral illness with no specific cure, orginating in the Zika Forest in Uganda around 60 years ago. It is spread by mosquitos active during the day (Aedes aegypti) as for Dengue Fever and Chikungunya. There are also reports of transmission via sexual activity. Areas affected include South America, Central Americas, North America, Caribbean, Samoa and other Pacific Islands – spreading quickly to other regions.

Symptoms are usually mild and appear a 2-7 days after the infecting bite:

• Fever

• Rash which becomes generalised

• Transient arthralgia, myalgia

• Conjunctivitis (red eyes).

• The illness is usually mild with symptoms lasting from several days to a week.

• Severe disease requiring hospitalization is uncommon;

• The virus stays in the blood for a few days (sometimes longer);

• Serious complications are possibly the risk of birth defects (microcephaly) and Guillain Barre Syndrome.

• Further research is being undertaken to establish the links between these two diseases and Zika. 
  
  

Dr. Spike Briggs is medical director of Medical Support Offshore and can be contacted at info@msos.org.uk

For further information, several websites are regularly updated with verified information:

NHS travel advice

Centre for Disease Control, USA – travel advice

WHO International Travel and Health

*Image credit:James Gathany via WikimediaCommons