Alarming spike in dengue cases

Dengue is a viral disease transmitted by infected mosquitoes. It usually begins with flu-like symptoms but can develop into a potentially lethal complication called ‘severe dengue’. It is found mostly in urban and semi-urban areas and has long been associated only with tropical and sub-tropical climates. However, climate change and shifting temperatures are now expanding the habitat of the mosquitoes that carry the disease, allowing them to spread further north. And since there is no specific treatment for dengue, the best way to prevent it is to protect against mosquito bites.

Situation report June 2024

Since the beginning of 2024, around 10 million dengue cases and over 5,000 dengue-related deaths have been reported to the WHO from more than 80 countries/territories worldwide. Most cases have been reported from countries in the Pan-American region, including Brazil (over eight million), followed by Argentina, Paraguay, Peru and Colombia. However, dengue circulation has been reported also from South-East Asia and Western Pacific, as well as in Africa. Furthermore, both mainland Europe and the US report of a substantial increase in number of imported cases of dengue since the beginning of 2024.

Symptoms to look out for

A seafarer infected by dengue may initially experience fever with mild non-specific symptoms like those of influenza and other febrile illnesses. However, according to the WHO, dengue can be suspected when a high fever (40°C/104°F) is accompanied by any of the following symptoms:

• severe headaches,

• pain behind the eyes,

• muscle, bone and joint pains,

• nausea or vomiting,

• swollen glands, or

• rash.

Symptoms usually last for 2-7 days, following an incubation period of 4-10 days after a bite from an infected mosquito.

Severe dengue is a potentially fatal complication due to plasma leaking, fluid accumulation, respiratory distress, severe bleeding, or organ impairment. The warning signs to look out for occur 3-7 days after the first symptoms in conjunction with a decrease in temperature (below 38°C/100°F) and include severe abdominal pain, persistent vomiting, rapid breathing, bleeding gums, blood in vomit, fatigue and restlessness. The next 24-48 hours of the critical stage can be fatal and proper medical care is needed to avoid complications and the risk of death. According to the CDC, approximately 1 in 20 patients with dengue progress to severe dengue.

Recommended precautions

As the global dengue situation may change rapidly, we recommend that ship operators monitor dengue situation reports and advice from public health officials, such as the:

• WHO’s Disease outbreak news (DON) and Global dengue surveillance dashboard. A separate overview is available for the Pan-American Region.

• CDC’s Health alert network (HAN) and Data and statistics on dengue in the United States.

• ECDC’s Dengue worldwide overview.

When vessels are trading to countries with ongoing dengue transmission, ensure that crews are informed about the risks and the precautions they should take to avoid mosquito bites. Make sure that sufficient supplies of effective insect repellents, light coloured boiler suits, porthole/door mesh screens and bed-nets are available onboard and stress that a headache, fever and flu-like symptoms are always grounds for contacting the medical officer.

For medical officers, we recommend consulting the diseases section of the Mariners Medico Guide app, to obtain up to date medical information and treatment support for dengue fever. In a case of a patient with clinically suspected dengue, it is particularly important to note that the use of NSAIDs, such as aspirin and ibuprofen, should be avoided due to the potential risk of bleeding.

Although, dengue vaccines have now been approved by the WHO, they are currently not widely used and primarily recommended for children living in endemic areas. We therefore recommend checking with a medical doctor if dengue vaccination is available for and needed for seafarers.

Our hot topic page Mosquito-borne disease precautions contains an overview of recommended precautions ship operator could implement prior to, during and after a vessel’s visit to a port affected by a dengue outbreak.