Zika-Fever Outbreak on the southern Cape Verde Islands
by Dr. Pitt Reitmaier - Tropical Hygiene and Medicine
In the beginning of November 2015 Zika-Virus as the cause of before unclear infections was proven on the Cape Verde Islands, for the first time in history, by serological lab-tests. (Institut Pasteur / Dakar)
Since September 2015 approximately 1,000 cases of an unknown virosis with rash, joint pain, non-purulent conjunctivitis, muscle and headache, pain behind the eyes, and vomiting, similar to mild forma of Dengue Haemorrhagic Fever had seeked assistence by the health services of the countrys capital Cidade da Praia. The vast majority of patients came from the urban areas of the city of Praia.
Zika-Virus disease is considered benign and heals spontaneously in about a week. Lethal cases and serious complications are extremely rare. Most infections show no or so mild symptoms that sufferers do not seek health services. The number of infection is about fife times higher than the Number of patients seen by health services.
To date there is no specific therapy nor a vaccine available.
Zika is considered an "emerging disease", fostered by climate change, intensive travel and littering in poor suburban settings. Litter is a favourable habitat for the transmitting misquito. The disease has spread to moderate clinate zones in the last years. In Miami / Florida / USA in summer 2016 a considerable number of authochtonous cases has been registerd. The is increasing evidence for an advanced process of adaptation to cooler, non-tropic temperatures for the asatic tiger mosquito stegomyia albipictus. In the districts of St. Georgen near Freiburg / Breisgau (Black forest) as in the district of Heidelberg, the mosquito was able to reproduce over the mild winter of 2015-16 from one year to the next.
In 2014/15/16 Zika-virus was the cause of an epidemic in Brazil with millions of cases. In North America and Europe imported cases were detected as well. The Ministry of Health of Brazil has postulated a relationship between Zika fever and a high incidence of microcephaly in neonates in late 2015. Concluding scientific evidence for a causal relationship is not available to date. Other frequent diseases and co-factores in the mother also lead to microcephaly among the newborn. In previous Zika epidemics in other countries cases of microcephaly were not followed up with the same attention. But evidence is growing and physicians can not wate for the final proof and must show ways to avoid and prevent an infection to pregnant women.
On 22 01 2016, US health authorities have released a provisional travel - warning for pregnant women under the impression of an autochthonous case of Zika-positive newborn with microcephaly that had occurred in Hawaii. Cape Verde, without distinction between affected and not affected islands, appeares on the list of Zika infection areas. The Foreign Office of the Federal Republic of Germany and travel-medicine-institutions in German language followed in May 2016 with a Merkblatt zu den Risiken durch Zika-Virus
The special importance of a Zika-Virosis-Outbreak
in the Cape Verde archipelago is not limited to the risk to aquire a relative mild disease and the much more important neurological consequences in the newborn. The mosquito-vector Stegomyia (formerly called aedes) can transmit even more dangerous diseases like Dengue, Chikungunya, Yellow Fever, West Nile Fever and other arbo-viroses. Where Zika viruses is transmitted, these diseases can be transmitted as well. Stegomyia mosquitoes use even smallest accumulations of water in sub-pots of flowers, in cans, bottles, plastic bottles, tetra packs and car tires in trashed cities and multiply even in polluted water. They are "civilization followers". World literature also refers to a small number of transmissions through unprotected sex in the world literature.
Geographical center of the epidemic
was the capital Praia with> 80% of cases of Santiago Island. As of ealry December 2015, the total number of clinically diagnosed cases had grown to 5,000 on the islands of Santiago, Maio and Fogo. By this time, the peak of the epidemic was passed in Santiago and the number of new cases per week declined. Fogo went on for a few weeks with constant numbers of new cases of ca 25 / day concentrated in the city of São Filipe .. On 30 01 2016 a secondary focus was reported from the village of Rabil on Boa Vista island that reached a total of 190 cases that quickly disappeared.
By end of January 2016 the peak of the epidemic curve had passed on all islands affected and it was expected that the seasonal drought would reduce it to a few singular cases by March - April 2016. So it occurred. Since June 2016 no more cases were observed.
Of the approximately 140 women who were diagnosed Zika cases during pregnancy,three children were born with microcephaly, two in Cabo Verde and one in the US. Serological tests show a link between Zika infection of mothers and their offspring.
- avoid mosquito-bites
- First suspected cases occurred In September 2015.
- As expected on a subtropical arid archipelago,the Zika virus outbreak only affected part of the islands.
- Origin and center was the capital Praia (> 120000 inhabitants.) In Santiago.
- Secondary centers of autochthonous transmission were the southern islands Maio and Fogo and briefly Rabil in Boa Vista.
- The northern islands have only seen afew imported cases, no autochthonous transmission.
- This geographic distribution corresponds well to the image, as it was found during the dengue outbreak of 2009 when Sal, São Nicolau, São Vicente and Santo Antao were only minimally or not affected at all.
- The readyness of the population to participate in cleaniing campaigns, is significantly lower than dur9ing the dengue epidemic 2009.
- The Zika-epidemic in Cabo Verde was caused by the same virus strain, which has been observed in Brazil 2014/15.
- in case you fall ill with a fever that might be Zika:
- wear light-coloured long trousers and long-sleeved blouses, shirts and socks.
- use mosquito nets, mosquito coils and air conditioning
- Apply repellents throughout the day.
- Take care of your immediate residencial environment, your house / flat in respect of waste and water pockets: Change all standing water accumulation in and around the household (flower vases, cisterns and siphons of sink, showers and toilets and, watering cans, mop bucket, gutters etc.) at least once a week.
- for pregnant women:
- use only Paracetamol as a pain-killer, no others, especially no ASS = Aspirin® and no Ibuprofen®.
- for couples without contraception / desiring a pregnancy:
- Shift to regions / islands without autochthonous transmission of the virus
- Delay the journey to the time after pregnancy
- if the trip can not be postponed, practice mosquito bite avoidance consequently.
- use condoms when sleeping with a partner who traveled to a Zika infection, until the end of pregnancy.
- Shift to regions / islands without autochthonous transmission of the virus
- Postpone the pregnancy to the time after the yourney
- Use condoms while in a Zika-Infection-area and for the followng 8 weeks
- in case you fall ill with a fever that might be Zika, postpone the pregrnacy for two years.
Who is who? Simplified practical information
Substances that shy organisms away (e.g., mosquitoes, fleas, ticks) by their smell, preventing bite or sting. In Cape Verde pharmacies, repellent with trackball as we know them from deodorants, are sold. On the uncovered skin, applied to the brim, trouser hem and cuffs, the effect last for 2-8 hours. The duration of action can be found in the package insert. Active ingredient: DEET
Fine, tight-closing net over the bed, usually impregnated to kill mosquitoes. The network is remained closed while the bed is not used, . Before going to bed open the net and stuck it under the mattress creating a completely tightly closed mosquito-free space. Bed nets are one of the most successful elements of the WHO strategy to reduce malaria.
Mosquitofish Gambusia affinis
Up to 7 cm long viviparous freshwater toothcarps from the same family as guppies. They endure the most adverse livingconditions and love to feed on moquito larvae (bloodworms). When used in water tanks, ponds and natural swimming pools, they keep them free of larvae . A reliable strategy for farms for farms, apartments, flats and gardens.
If transmission of a disease pathogen from those already infected (animals or humans = reservoir) to the host is done by an animal, such as a mosquito, a tick, a bug or fly, the latter is called vector. Of particular importance are mosquitoes in the transmission of parasites (eg. Malaria) or viruses (eg. Dengue). Both obligatoriliy multiply in the mosquito and in the human host, so that the presence of the vector is a prerequisite of transmission in an environment suitable for replication (water retention, temperature, humidity).
Mosquito control takes place both in the larval stage in the water and against flying mosquitoes.
Stegomyia formerly Aedes
Day and where artificial lighting is sufficient, even nocturnal mosquitoes able to transmit Zika virus, Dengue fever, Yellow fever, Chikungunya, West Nile Fever and other arbo-viruses. Their habitat is limited to tropical and subtropical regions at altitudes up to 2000m. Infected mosquitoes transmit the virus on to their eggs (vertical transmission) so that even after more than a year still infected larvae / mosquitoes incur. The larvae live in small pools of water, under pots, in bottles and plastic bottles in empty cans, tetra packs and tires, in the cisterns of unused toilets - to name just some examples. The larvae are undemanding regarding water purity and quality. The adults do not fly far, so that as a rule the mosquitoes, of which one is engraved, come out of your own home or from neighbouring flats. With the bite the female mosquito injects a pain-relieving substance, so that the nuisance caused by the stings is low or it is not notable. Suburbian landscapes with a lot of litter are particularly affected, and the elimination of waste in the countryside and change of all standing water accumulation in and around the household (flower vases, cisterns and siphons of sink, showers and and toilets, watering cans, mop bucket, gutters etc.), at least once a week, are the most important measure to combat mosquitoes. In Cape Verde Stegomyia aegypti is known for centuries, while Stegomyia albopictus the Asian tiger mosquito was not encountered yet.
Crepuscular and nocturnal mosquitoes that can transmit malaria. The occurrence is not limited to tropical regions. In temperate climate strong populations exist, that in earlier centuries have caused malaria epidemics in the Rhine Valley, in Canada and Lapland. The Anopheles in CapeVerde are predominantly zoophile, which means that they prefer to bite animals and and only exceptionally people. Since a female mosquitoe must feed twice in a human to pass on the disease, this explains why only few cases occur even when mosquito populations grow strong in a rainy season.
The spreading of an (infectious) disease as it was unexpected in time, geographical pattern and frequency. Infectious diseases spread in populations, while per infected individual on average more than one individual gets infected. If it is possible to reduce the transmissions by treatment and isolation of the infected / sick, by barriers (repellents and nets) by control of vectors (mosquitoes), by mass vaccinations or simply by the fact that almost the entire population has undergone the disease and therefore immune, the epidemice ends.
An individual,, having suffered from an infectious disease onde, may not aquire this disease again. Many viral diseases like Yellow fever, Dengue and Zika leave a lasting immunity behind. This may even happen, when the infection was inapparent, say without symptoms.
An individual receives a vaccine and becomes immune to a certain disease.
In active immunization living or dead pathogens (or parts of them) are administered to the body reacts and builds a more or less permanent immunity.
In passive immunization substances (immunoglobulins / antitoxins), produced by other humans or animals are administered to the individual to get protected for the time the concenrtration of the immunoglobulins / antitoxins is suffiently high.
Against Yellow Fever there is a well-tolerated effective vaccine available, while against Dengue and malaria vaccines are in development. The declaration of Zika-Virus as an international health-emergency by WHO allows to fincance the development of a vaccine for the first time.
All information to the best of our knowledge and belief - No warranty !
For individual recommendation, please contact your physician!