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22 July 2024

Situation at a glance

On 14 June 2024, the Ministry of Health and Medical Education (MoHME) of Iran reported the first two locally acquired cases of dengue recorded in the country. Local transmission of dengue within the community was confirmed in Bandar-Lengheh, Hormozgan Province, southern Iran. As of 17 July 2024, the total number of locally acquired (autochthonous) dengue cases in the country has risen to 12, all reported in Bandar-Lengheh. Dengue is a mosquito-borne viral disease caused by the dengue virus, with the potential to cause a serious public health impact. The primary vectors that transmit the disease are mosquitos of the Aedes genus, primarily Aedes aegypti and, to a lesser extent, Aedes albopictus. Iran’s MoHME has enacted measures to strengthen hospital readiness. The World Health Organization (WHO) is supporting the MoHME to enhance surveillance, distributing medical and rapid diagnostic supplies, providing training, and organizing risk communication and community engagement (RCCE) activities. On 16 May 2024, WHO reassessed the global risk of dengue as high, reiterating that dengue remains a global public health threat. The risk for Iran is also high due to the presence of the vector in the country, favourable climate conditions for the vector and the movement of people from countries with ongoing dengue outbreaks and endemic areas to Iran.

Description of the situation

 

On 14 June 2024, the Ministry of Health and Medical Education (MoHME) of Iran reported local transmission of dengue in Bandar-Lengheh, Hormozgan Province, within southern Iran.

Two cases of dengue, without any history of travel outside Iran, were confirmed through Polymerase Chain Reaction (PCR) testing conducted by the Arbovirus laboratories of the Pasteur Institute in Bandar Abbas.

By 17 July 2024, a total of 12 autochthonous cases of dengue have been documented in Iran, all of which were reported in Bandar-Lengheh, Hormozgan Province.

Iran had been reporting an average of 20 imported dengue cases annually between 2017 and 2023. However, there was a significant increase in imported dengue cases in 2024, with 137 reported between 15 May and 10 July.

This represents the first report of autochthonous dengue cases in Iran. The confirmation of local dengue virus transmission in 2024 is therefore an unusual although expected event due to the presence of the vector in the country and movement of people from endemic areas to Iran.

Based on entomological surveillance, to date, Aedes aegypti and some Aedes albopictus mosquitoes are established in the provinces of Sistan and Balouchistan, Hormozgan, Bushehr, Khuzastan, and Gilan.

In the WHO Eastern Mediterranean Region, dengue outbreaks continue to be reported in both fragile, conflict-affected, and/or vulnerable countries in the region that have weakened healthcare systems as well as countries with stronger healthcare systems that have been affected by unusual rains due to climate change. Ae. aegypti and some Ae. albopictus mosquitoes have been identified in most of the countries in the region.

 

Epidemiology

Dengue is a mosquito-borne viral disease caused by the dengue virus (DENV), with the potential to cause a serious public health impact. Dengue infections are the most common vector-borne viral infections worldwide, particularly impacting tropical and subtropical countries. The virus is primarily transmitted through the bite of infected Aedes mosquitoes, most commonly Aedes aegypti and Aedes albopictus. The proliferation and propagation of mosquitoes depend on climatic factors such as temperature, humidity and rainfall. The virus can be carried by infected travelers (imported cases) and may establish new areas of local transmission where there is a susceptible population and the local presence of vectors.

DENV has four serotypes (DENV-1, DENV-2, DENV-3, DENV-4). Infection with one serotype provides long-term immunity to the same serotype and short-term immunity to the other serotypes, after which secondary infections with a different serotype increase the risk for severe dengue. Dengue cases are most commonly asymptomatic or result in mild febrile illness. However, some cases will develop severe dengue, which may involve shock, severe bleeding or severe organ impairment. This stage often starts after the fever has gone away and it is preceded by warning signs such as intense abdominal pain, persistent vomiting, bleeding gums, fluid accumulation, lethargy or restlessness, and liver enlargement.

There is no specific treatment for dengue, but the timely diagnosis of dengue cases, identification of warning signs for severe dengue, and appropriate clinical management are key elements of care to prevent the progression to severe dengue and deaths. WHO recommends the TAK-003 dengue licensed vaccine in children aged 6–16 years in settings with high dengue transmission intensity.

Public health response

The MoHME has implemented measures to enhance hospital readiness in response to the emerging threat of dengue. The comprehensive approach aims to prepare outpatient and hospital staff for effective diagnosis and treatment of cases. The MoHME has identified eight high-risk provinces for targeted intervention based on vector density and the number of reported cases: Baluchistan, Bushehr, Fars, Gilan, Golestan, Hormozgan, Khuzestan, Mazandaran and Sistan.

With the support of WHO, targeted dengue interventions are underway, including:

  • Strengthening laboratory and hospital-based disease surveillance in all affected provinces and at the national level.
  • Providing validated diagnostic supplies and medicines for managing the symptoms, to ensure the continuity of essential care.
  • Providing pesticides, and long-lasting insecticide-treated nets for control measures.
  • Training healthcare workers in case management and entomologists in vector surveillance and control.
  • Collaborating with partners including national and provincial health ministries regarding community awareness campaigns by providing RCCE materials and organizing advocacy campaigns.
  • Establishing an inter-agency team to coordinate activities and providing technical and operational support to the MoHME.
  • Conducting technical meetings with the participation of the Vector Borne Disease department of the MoHME and the regional advisor.

WHO risk assessment

This represents the first report of autochthonous dengue cases ever documented in Iran. The confirmation of local dengue transmission in 2024 is thus an atypical yet foreseeable event due to the presence of the vector in the country and the movement of people from endemic areas to Iran.

Based on entomological surveillance, to date, Aedes aegypti and Aedes albopictus are present in the provinces of Baluchistan, Bushehr, Fars, Gilan, Golestan, Hormozgan, Khuzestan, Mazandaran and Sistan.

On 16 May 2024, WHO reassessed the global risk of dengue, confirming it to be high and emphasizing that dengue continues to pose a significant public health threat worldwide.

The national risk for Iran is also high due to the presence of the vector in the country, favorable climate conditions for the competent vector and the movement of people from countries experiencing ongoing outbreaks and endemic areas to Iran. There is heightened awareness of the potential increase in importations and subsequent transmission of the disease during the upcoming Arbaeen pilgrimage in August, when millions of people from different countries, including countries reporting dengue cases travel to Iran.

WHO advice

The proximity of mosquito vector breeding sites to human habitation is a significant risk factor for dengue virus infection. Aedes species mosquitoes can become infected with the virus after biting individuals infected with DENV and then transmit the virus to others in the vicinity. This cycle, therefore, makes the infective mosquito capable of spreading the dengue virus within households and in the neighborhoods of cases, leading to clusters. An integrated approach including all the components for preparedness, prevention and control of dengue is needed as outlined in the Global Arbovirus Initiative.

Effective vector control interventions are key to the prevention and control of dengue. Vector control activities should target all areas where there is a risk of human-vector contact, such as residences, workplaces, schools, and hospitals. WHO promotes Integrated Vector Management to control Aedes species, including removing potential mosquito breeding sites, reducing their populations, and minimizing individual exposure. This should involve vector control strategies for larvae and adults (i.e., environmental management and source reduction), especially monitoring water storage practices, draining and cleaning household water storage containers weekly, larvicide in non-potable water using WHO-prequalified larvicides at correct dosages, distribution of insecticide-treated nets for fever/dengue inpatients to contain the spread of the virus from health facilities. Indoor space spraying for rapidly containing dengue-infected mosquitoes may be challenging to deliver in densely populated urban areas.

Personal protective measures are recommended from dawn to dusk due to the diurnal Aedes aegypti. During outdoor activities, personal protective measures recommended include topical repellents to exposed skin or the treatment of clothing and using long-sleeved shirts and pants. Indoor protection can include the use of household insecticide aerosol products, or mosquito coils during the day; window and door screens can reduce the chances of mosquitoes entering the house and insecticide-treated nets offer good protection to people against mosquito bites while sleeping during the day. These measures and mosquito control should also cover workplaces and schools since the vectors are day-biting mosquitoes. Entomological surveillance should be undertaken to assess the breeding potential of Aedes mosquitoes in containers to target vector control activities and monitor insecticide resistance to help select the most effective insecticide-based interventions.

There is no specific treatment for dengue infection. However, early detection and access to appropriate healthcare for case management reduces mortality, as can rapid detection of dengue cases with warning signs and timely referrals of severe cases to tertiary healthcare facilities. Case surveillance should continue to be enhanced in all affected countries and globally. Where feasible, resources should be allocated for the strengthening of case referral mechanisms and for the confirmation and serotyping of the dengue viruses.

TAK-003 is a licensed dengue vaccine, and WHO currently recommends its use in children aged 6–16 years in settings with high dengue transmission intensity. WHO recommends that countries consider introducing TAK-003 into their routine immunization programmes in geographical locations where high transmission intensity of dengue poses a significant public health problem.

WHO does not currently recommend the programmatic use of TAK-003 in children aged <6 years because of the lower efficacy of the vaccine in this age group.

WHO, recommends that vaccination against dengue must be part of an integrated strategy to control the disease, including vector control, proper case management, community education, and community engagement.

Countries are encouraged to adopt effective case management, prevention and control of dengue and other arboviruses, and share their experience through heightened research projects, particularly given the recent WHO recommendations on clinical trials. Implementing clinical surveillance and case and death report forms for dengue could be particularly useful in understanding the disease better and also form a basis for developing clinical trials for new therapies or quality improvement initiatives.

In light of recent outbreaks of dengue virus infection and ongoing transmission in multiple regions where Aedes aegypti and Aedes albopictus mosquitoes are present, WHO has compiled information for travellers to be aware of the risk of transmission and take steps to protect themselves from infection.

WHO does not recommend any general travel or trade restrictions based on the available information.

Further information

 

Citable reference: World Health Organization (22 July 2024). Disease Outbreak News; Dengue – Iran (Islamic Republic of). Available at: https://www.who.int/emergencies/disease-outbreak-news/item/2024-DON526

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