Situation at a glance

Between 1 January and 27 September 2022, a total of 25 932 confirmed dengue cases and 62 deaths (CFR 0.25%) were reported in Pakistan, with 74% of these cases reported in the month of September alone. The current surge in cases follows unprecedented flooding that began in mid-June 2022. With the current flood crisis affecting the national health system capacity and the growing humanitarian situation, there is a high risk of serious health impacts from dengue fever and other concurrent disease outbreaks. High population movement between Pakistan and bordering countries (in particular, Afghanistan and the Islamic Republic of Iran) means that the international transmission of dengue fever cannot be ruled out.

Description of the outbreak

Dengue fever is endemic to Pakistan, which experiences year-round transmission with seasonal peaks. However, triggered by the worst flooding in the country’s history that began in mid-June, the number of reported dengue cases is significantly higher in 2022 (between January and September) as compared to the same period during the four previous years.

Between 1 January to 27 September 2022, according to the National Institute of Health-Islamabad, a cumulative total of 25 932 confirmed dengue cases and 62 deaths have been reported nationally. Three-quarters (74%) of these cases were reported during the month of September alone. As of 22 September, the distribution of cases by province was available for 83% (n=21 777) of the total cases, of which 32% (n=6888) were reported from Sindh, 29% (n=6255) from Punjab (including the Islamabad Capital Territory), 25% (n=5506) from Khyber Pakhtunkhwa, and 14% (n=3128) from Balochistan (Figure 1).

Figure 1. Distribution of confirmed dengue cases in Pakistan by province, 1 January to 22 September 2022.Epidemiology of dengue

Dengue is a viral infection transmitted by mosquitoes caused by four types of dengue virus (DENV 1, DENV 2, DENV 3, DENV 4). Infection with one serotype provides long-term immunity to the homologous serotype, but not to other serotypes; sequential infections put people at greater risk of severe dengue. DENV can cause an acute flu-like illness, many DENV infections produce only mild illness; over 80% of cases are asymptomatic.

There is no specific treatment for dengue, however, timely detection of cases, identifying any warning signs of severe dengue infection, and appropriate case management are key elements of care to prevent patient death and can lower fatality rates of severe infection to below 1%.

Dengue fever is endemic in Pakistan, with seasonal outbreaks and the circulation of the four serotypes in different areas of the country. Aedes aegypti and Aedes albopictus are widely adapted vectors for urban and peri-urban environments. As dengue is recurrent in the country, the population may be at risk of re-infection and therefore, serious complications may occur if not managed promptly and correctly.

Public health response

The Ministry of Health, in collaboration with the Global Fund, is conducting vector surveillance and control activities as a part of Integrated Vector Management, including:

• Technical weekly committee meetings chaired by the Ministry of Health.
• Activation of ‘dengue counters’ in all health facilities; designated areas in emergency departments allocated for receiving suspected dengue cases.
• Enhancement of vector surveillance activities in Lahore and other districts.
• Provision of additional teams to support vector surveillance activities including the daily situation analysis.

The WHO is providing support including:

• Coordination at multiple high-level meetings for health authorities including visits and meetings of the WHO representative.
• Strengthening of laboratory and hospital-based disease surveillance across all provinces in the country has been initiated.
• Training of selected health care providers from all provinces in the country is being held on case management of dengue fever.
• Training on vector surveillance and vector control including source reduction during house visits is underway.
• Provision of 230 000 rapid diagnostic tests (RDTs) for dengue and other diseases, including malaria, acute watery diarrhoea, chikungunya, hepatitis A and E.

WHO risk assessment

Pakistan is experiencing an abnormal monsoon rainfall and unprecedented floods. One-third of the country and an estimated 33 million people have been impacted in 84 calamity declared districts. More than 2 million houses have been destroyed and an estimated 1460 health facilities have also reportedly been damaged. Some 7.9 million people are reportedly displaced, 12 900 people injured, and 1600 people have died. Heavy rains and floods have left millions of people without access to healthcare and medical treatment.

With the current flood crisis affecting the national health system capacity, there is a high risk of serious health impacts from dengue fever.  Currently, there is a need for improved vector surveillance, enhanced laboratory capacity for better detection, sensitization of health care providers on case management (including warning signs of severe dengue) and improved surveillance of acute febrile illness to better define disease burden and seasonality patterns.

Vector-borne epidemics – including dengue – after flooding is a well-known phenomenon, as the stagnant water provides favorable habitats for mosquitoes to breed. The lag time is usually around 3-4 weeks before the occurrence of dengue cases.

Ongoing disease outbreaks in Pakistan, including acute watery diarrhoea, dengue, malaria, measles, polio, and COVID-19 are being further aggravated, particularly in internally displaced persons and refugee camps and where water and sanitation facilities have been damaged.

Dengue fever is the most rapidly spreading mosquito-borne virus infection in the world. There is high population movement between Pakistan—in particular, Khyber Pakhtunkhwa province— and bordering countries, especially the Islamic Republic of Iran and Afghanistan. Khyber Pakhtunkhwa province is also home to 1 200 000 Afghani refugees, of which 800 000 live in districts officially notified as calamity hit by floods. The transmission of dengue fever from Pakistan to border countries cannot be ruled out.

WHO advice

The proximity of mosquito vector breeding sites to human habitation is a significant risk factor for dengue virus infection. There is no specific treatment for dengue infection, but early detection and access to appropriate healthcare reduce mortality. Furthermore, the prevention and control of dengue depend on effective vector surveillance and control. 

WHO promotes the strategic approach known as Integrated Vector Management (IVM) to control mosquito activity and population, including Aedes spp. (the vector of dengue). 

IVM activities should be enhanced to remove potential breeding sites, reduce vector populations, and minimize individual exposure. This should involve vector control strategies for larvae and adults (i.e. environmental management and source reduction, and chemical control measures), as well as strategies for protecting people and households. Vector control activities should focus on all areas where there is human-vector contact (place of residence, workplaces, schools and hospitals). 

Vector control activities can include covering, draining and cleaning household water storage containers on a weekly basis. In addition, this may include chlorination of drinking water and application of suitable larvicides/insecticides for water storage in outdoor containers. 

Where indoor biting occurs, application of mosquito repellent lotion or sprays on the skin, use of household insecticide aerosol products, mosquito coils, or other insecticide vaporizers are recommended. Household fixtures such as window and door screens and air conditioning can also reduce bites. Since Aedes spp mosquitoes (the primary vector for transmission) are day biters with peak activity at dawn and dusk, personal protective measures such as the use of clothing to minimize skin exposure are recommended. During outdoor activities, mosquito repellents may be applied to exposed skin or to clothing. Insecticide-treated nets offer good protection to people who sleep outside or during the day (e.g. infants, people confined to bed, and night workers) and at night to prevent mosquito bites. 

In addition, vector and human case surveillance should continue to be enhanced in all affected areas and across the country. Key public health messages on reducing the risk of dengue transmission among the population are expected to continue to be provided. 

WHO does not recommend any general travel or trade restrictions to Pakistan based on the information available for this event.

Further information

References:

• WHO dengue factsheet: https://www.who.int/news-room/fact-sheets/detail/dengue-and-severe-dengue
• WHO Q&A: Dengue and severe dengue: https://www.who.int/news-room/questions-and-answers/item/dengue-and-severe-dengue
• WHO Health topics: Dengue and severe dengue https://www.who.int/health-topics/dengue-and-severe-dengue#tab=tab_1
• UN OCHA PAKISTAN: Monsoon Floods Situation Report No. 6 As of 16 September 2022: https://reliefweb.int/report/pakistan/pakistan-2022-monsoon-floods-situation-report-no-6-16-september-2022

Citable reference: World Health Organization (13 October 2022). Disease Outbreak News; Dengue - Pakistan. Available at: https://www.who.int/emergencies/disease-outbreak-news/item/2022-DON414