Tuesday, September 06, 2016

HK CHP Investigating 3rd Locally Acquired Case Of Dengue Fever


Although Zika is garnering most of the headlines, it is far from the only arbovirus on the move around the globe.  Yellow Fever, Japanese Encephalitis, Chikungunya, and Dengue fever - all transmitted by mosquitoes - are making inroads around the world.

In Hong Kong Dengue viremic travelers arrive nearly every week, but local transmission is rare.  In 2015, HK reported 2 locally acquired cases, while in 2014 they reported 3. 

But with a competent local vector, and a continual re-seeding of the virus into that population, there is always a concern that the virus will get a firm foothold into the region and become endemic.

In August Hong Kong reported 2 locally acquired cases, and now announces a 3rd.  An investigation is now underway to determine if these cases are related, or are separate incidents. 

     The Centre for Health Protection (CHP) of the Department of Health (DH) is today (September 6) investigating a local case of dengue fever (DF), and hence again urged the public to maintain strict environmental hygiene, anti-mosquito  and personal protective measures both locally and during travel.

     The female patient, aged 40 with underlying illness, has presented with fever, headache, muscle pain, vomiting and diarrhoea since August 27. She attended Ruttonjee Hospital (RH) and was admitted on August 29 and discharged today. She has all along been in stable condition.

     Testing of her blood specimen by the CHP's Public Health Laboratory Services Branch today confirmed dengue virus infection.

     Initial enquiries revealed that the patient lives in Conduit Road, Mid-levels. She had no recent travel history. During the incubation period, the patient had visited Graham Street Market almost daily via the Central-Mid-Levels Escalator and Walkway System.

     Her home contacts have remained asymptomatic so far and have been put under medical surveillance.

     "The CHP immediately commenced epidemiological investigations and promptly informed the Food and Environmental Hygiene Department (FEHD) for vector investigation and mosquito control. Investigations and health education in vicinities where the patient frequented are proceeding," a spokesman for the CHP said.

     Officers of the CHP will conduct site visit and field investigations by questionnaire surveys at the patient's residence for active case finding and arranging blood tests.

     "Further to the first two locally acquired DF cases this year reported in August, we are conducting extensive investigations with FEHD to ascertain if this case is linked with the previous two cases with a view to controlling the possible spread," the spokesman said.

     Persons who have been to the vicinity of Conduit Road, Central-Mid-Levels Escalator and Walkway System, Shelley Street, Hong Kong Zoological and Botanical Gardens and Graham Street Market with DF symptoms should call the CHP's hotline (2125 2266) for laboratory investigation or referral as appropriate. The hotline will operate from 9am to 6pm between Monday and Friday to receive enquires.

     To date, 87 DF cases have been confirmed in 2016, comprising 84 imported and three local cases. In 2015, there were 114 cases, comprising two local, 110 imported and two unclassified cases. In 2014, there were 112 cases, including three local and 109 imported cases.

     "We will issue letters to doctors and hospitals to alert them to the case. We will also enhance surveillance of suspected cases in collaboration with public and private hospitals as well as private doctors. Early referral and prompt control are critical to prevent further local spread," the spokesman said.

     DF is transmitted to humans through the bites of infective female Aedes mosquitoes. The public are reminded to follow anti-mosquito measures when travelling to areas where DF is endemic in order to prevent DF. When a patient suffering from DF is bitten by a vector mosquito, the mosquito is infected and it may spread the disease by biting other people. In Hong Kong, the principal vector, Aedes aegypti, has not been found in recent years but Aedes albopictus is widely present so there is a risk of secondary spread of DF from imported infections.

     Dengue viruses encompass four different serotypes. The symptoms of first infection with one serotype are usually mild, but subsequent infections with other serotypes even years afterward are more likely to result in severe dengue, also known as dengue haemorrhagic fever. Severe dengue is serious and potentially fatal. Without proper treatment, the case fatality rate of severe dengue can exceed 20 per cent.

     "At present, there is no locally registered dengue vaccine available in Hong Kong. Strict environmental hygiene, mosquito control and personal protective measures remain the most effective means against DF both locally and during travel," the spokesman added.

     Travellers are urged to be alert to the dengue risk of travel destinations before departing and to take heed of the preventive measures below:

  • Wear loose, light-coloured, long-sleeved tops and trousers, and use DEET-containing insect repellent on exposed parts of the body and clothing;
  • Avoid using fragrant cosmetics or skin-care products and re-apply insect repellent according to instructions during outdoor activities;
  • Before the trip, arrange a travel health consultation at least six weeks in advance for any extra measures against mosquito bites;
  • During the trip, carry a portable bed net and apply permethrin (an insecticide) on it in rural endemic areas. Permethrin should not be applied to the skin; and
  • After returning from dengue endemic areas, continue to apply insect repellent for 14 days.

     The incubation period of DF ranges from three to 14 days, commonly four to seven days. Anyone feeling unwell after returning from a trip should seek medical advice as soon as possible and provide travel details to their doctor.

     Members of the public should also prevent the accumulation of stagnant water and maintain good environmental hygiene:

  • Change the water in vases once a week;
  • Clear the water in saucers under potted plants every week;
  • Cover water containers tightly;
  • Ensure air-conditioner drip trays are free of stagnant water;
  • Put all used cans and bottles into covered dustbins; and
  • Store food and dispose of garbage properly.

(Continue . . . )

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