• Yellow fever occurs in sub-Saharan Africa and South America and is transmitted by mosquitoes.
• Disease may be severe in unvaccinated travelers and death may occur in over 50%.
• A highly effective vaccine is available.
• Due to potentially severe side effects the vaccine is used with caution in immunocompromised or elderly individuals, as well as in pregnant women.

As against all mosquito-borne diseases, prevention from mosquito bites is during day and night (see “Insect and tick bite protection” factsheet). The available vaccine is highly efficacious and provides a long-term protection. It is recommended for people aged 9 months or older who are travelling to yellow fever endemic areas. In addition, providing proof of vaccination may be mandatory for entry into certain countries.

The vaccine is a live-attenuated form of the virus. In immunocompetent persons, protection starts about 10 days after the first vaccination. Reactions to yellow fever vaccine are generally mild and include headache, muscle aches, and low-grade fevers.  Side effects can be treated with paracetamol but aspirin and other nonsteroidal anti-inflammatory drugs, for example ibuprofen or naproxen, should be avoided.  On extremely rare occasions, people may develop severe, sometimes life-threatening reactions to the yellow fever vaccine – which is why this vaccine is used with caution in immunocompromised individuals, pregnant women and the elderly for safety reasons. Talk to your travel health advisor if you belong to this group.

• Dengue fever is the world's most common insect-borne infectious disease.
• Great attention should be paid to mosquito protection during the day!
• The disease can cause high fever, muscle and joint pain, and skin rashes. In rare cases, bleeding may occur. There is no specific treatment. Vaccination is recommended only for people with evidence of previous dengue infection.
• For personal safety, we strongly recommend that you inform yourself in detail about dengue.

Dengue fever is the most common insect-borne infectious disease worldwide. There are 4 known serotypes of dengue virus, so it is possible to be infected with dengue more than once. Approximately 1 in 4 infected individuals develop symptoms of dengue, resulting in high fever, muscle and joint pain, and skin rash. In rare cases, most often after a second infection, life-threatening bleeding and shock (severe drop of blood pressure) may occur.

In 3 out of 4 cases, an infection with the virus remains asymptomatic. After a short incubation period (5-8 days), 1 out of 4 infected people present an abrupt onset of fever, headache, joint, limb and muscle pain, as well as nausea and vomiting. Eye movement pain is also typical. A rash usually appears on the 3rd or 4th day of illness. After 4 to 7 days, the fever finally subsides but fatigue may persist for several days or weeks.

In rare cases, severe dengue can occur. Particularly susceptible are local children and seniors as well as people who have experienced a prior dengue infection. Tourists extremely rarely present with severe dengue. In the first days, the disease resembles the course of classic dengue fever, but on the 4th/5th day, and usually after the fever has subsided, the condition worsens. Blood pressure drops, and patients complain of shortness of breath, abdominal discomfort, nosebleeds, and mild skin or mucosal hemorrhages. In the most severe cases, life-threatening shock may occur.

There is no specific treatment for dengue virus infection. Treatment is limited to mitigation and monitoring of symptoms: fever reduction, relief of eye, back, muscle and joint pain, and monitoring of blood clotting and blood volume. Patients with severe symptoms must be hospitalised.

For treatment of fever or pain, paracetamol or acetaminophen are recommended (e.g. Acetalgin® Dafalgan®). Drugs containing the active ingredient acetylsalicylic acid (e.g. Aspirin®, Alcacyl®, Aspégic®) must be avoided.

Effective mosquito protection during the day and especially during twilight hours (i.e. sunset) is the best preventive measure:

1. Clothing: Wear well-covered, long-sleeved clothing and long pants and treat clothing with insecticide beforehand (see factsheet “prevention of arthropod bites”).
2. Mosquito repellent: Apply a mosquito repellent to uncovered skin several times a day (see factsheet “prevention of arthropod bites”).
3. Environmental hygiene: Do not leave containers with standing water (coasters for flower pots, etc.) in your environment to avoid mosquito breeding sites.

For further information, please refer to the factsheet on "Mosquito and tick bite protection".

Note on the dengue vaccine Qdenga®:

• Based on the data available, many European countries, as well as the Swiss Expert Committee for Travel Medicine (ECTM), currently recommend vaccination with Qdenga® only for travelers who have evidence of a previous dengue infection and who will be exposed in a region with significant dengue transmission. This is a precautionary decision, since the current data also include the possibility that people who are vaccinated with Qdenga® before a first dengue infection may experience a more severe course of the disease. A consultation with a specialist in tropical and travel medicine is recommended.

Consistent mosquito protection during the day (see above) is still considered the most important preventive measure against dengue!

Of note

• Do not take any products containing the active ingredient acetylsalicylic acid (e.g. Aspirin®, Alcacyl®, Aspégic®) if you have symptoms, as they increase the risk of bleeding in the event of a dengue infection!
• However, do not stop taking medications containing acetylsalicylic acid if it is already part of your regular treatment for an underlying condition.

• Do not take any products containing the active ingredient acetylsalicylic acid (e.g. Aspirin®, Alcacyl®, Aspégic®) if you have symptoms, as they increase the risk of bleeding in the event of a dengue infection!
• However, do not stop taking medications containing acetylsalicylic acid if it is already part of your regular treatment for an underlying condition.

• Chikungunya is a viral disease transmitted by Aedes mosquitoes.
• Chikungunya can be prevented by protection against mosquito bites.
• It typically presents with severe joint pain of the hands and feet. In a few patients, these may persist for weeks or months.

The infection may present with some or all of the following symptoms: sudden onset of high-grade fever, chills, headache, redness of eyes, muscle and joint pain, and rash. The rash usually occurs after the onset of fever and typically involves the trunk and extremities, but can also include the palms, soles of the feet, and the face.

Often fever occurs in two phases of up to one week duration, with an interval of one to two fever-free days in between. The second phase may present with much more intense muscle and joint pain, which can be severe and debilitating. These symptoms are typically bilateral and symmetric and mainly involve hands and feet, but may also involve the larger joints, such as the knees or shoulders.

About 5-10% of infected people continue to experience severe joint pain even after the fever has subsided, in some cases lasting up to several months or, albeit rare, even years.

• FOPH Switzerland: https://www.bag.admin.ch/bag/de/home/krankheiten/krankheiten-im-ueberblick/chikungunya.html
• WHO - Chikungunya fact sheet: https://www.who.int/news-room/fact-sheets/detail/chikungunya
• Center for Disease Control and Prevention (CDC): https://www.cdc.gov/chikungunya/index.html
  

• Marburg virus disease is a rare but severe hemorrhagic fever.
• The disease spreads through contact with infected animals or people.
• Symptoms can be similar to other tropical diseases
• There is no licensed treatment or vaccine for Marburg disease, and
• Prevention measures are important to follow, see below.

The incubation period (time between infection and onset of symptoms) ranges from a 2 to 21 days (usually 5 to 10 days). The onset of MVD is usually abrupt, with initially non-specific, flu-like symptoms such as a high fever, severe headache, chills and malaise. Rapid worsening occurs within 2–5 days for more than half of patients, marked by gastrointestinal symptoms such as anorexia, abdominal discomfort, severe nausea, vomiting, and diarrhoea. As the disease advances, clinical manifestations can become more severe and include liver failure, delirium, shock, bleeding (hemorrhaging), multi-organ dysfunction and death.

In case of symptoms

If think that you have had an exposure at risk and develop fever with nonspecific symptoms such as chills, headache, muscle pain, malaise or abdominal pain:

• you should separate yourself from others (isolate) immediately and
• immediately seek medical advice by contacting the in-country hotline by phone or contact a tropical institute or university hospital infectious disease unit.
• alert the healthcare providers of your recent travel to an area with a Marburg outbreak.

The risk for travellers is  very low if the below precautions are followed, but it is high for family members and caregivers who have contact with sick people.

General precautions during travel to affected areas:

• Wash your hands regularly and carefully using soap and water (or alcohol gel if soap is unavailable).
  
• Avoid contact with sick people who have symptoms, such as fever, muscle pain, and rash.
  
• Avoid contact with blood and other body fluids
  
• Avoid visiting healthcare facilities in the MVD-affected areas for nonurgent medical care or non-medical reasons.
  
• Avoid contact with dead bodies or items that have been in contact with dead bodies, participating in funeral or burial rituals, or attending a funeral or burial. 
  
• Avoid handling, cooking, or eating bush/wild meat (meat of wild/feral mammals killed for food).
• Wash and peel fruit and vegetables before consumption.
  
• Avoid visiting mines or bat caves and contact with all wild animals; alive or dead, particularly bats.
  
• If you decide to visit mines or caves inhabited by fruit bat colonies, wear gloves and other appropriate protective clothing, including masks and eye protection.
  
• Practice safer sex.

• Swiss Federal Office of Public Health: LINK
  
• European Center for Disease Control and Prevention (ECDC): Marburg virus disease
  
• US Center for Disease Control and Prevention (CDC): About Marburg Disease
• World Health Organization: Marburg Virus Disease

• Mpox is a viral disease that typically causes a rash, swollen lymph nodes and fever.
• An emerging variant is spreading rapidly in eastern D.R. Congo and neighboring countries prompting a new WHO declaration of a public health emergency of international concern (PHEIC), as of August 14th 2024.
• Close physical contact (sexual or non-sexual) is the main mode of transmission.
• The disease generally follows a mild course. Children, pregnant women, and people with weak immune systems are the most at risk of complications.
• Vaccination against mpox is available, but limited to groups at high risk of exposure. 

Mpox has been commonly found in West and Central Africa for many years where the suspected reservoir - small mammals - is endemic. There are two types of Monkeypox virus called ‘clades’ that cause the disease mpox - clade I in Central Africa and clade II in West Africa. Since the end of smallpox vaccination campaigns in the early 1980’s, cases of mpox have increased, slowly at first and significantly in the last 5-10 years, especially in the Democratic Republic of Congo (DRC).

In 2022, a new emerging subclade of clade II was responsible for a global epidemic that spread mainly through sexual contact among men who have sex with men. It resulted in the first public health emergency of international concern (PHEIC) declared by the WHO until 2023. Although the clade II epidemic is now under control, this virus variant continues to circulate worldwide.

In 2024, the continued spread of mpox clade I in endemic regions of Central Africa, particularly in the DRC, and the emergence of a new subclade Ib in Eastern DRC and neighboring countries have raised global concern and prompted the WHO to declare a PHEIC for the second time in two years. The current geographical spread of the mpox clade Ib variant occurs via commercial routes through sexual contact (e.g. sex workers), followed by local transmission in households and other settings (which is becoming increasingly important).

Animal to human transmission
Mpox can spread from animal to human when they come into direct contact with an infected animal (rodents or primates).

Human to human transmission
Mpox can be spread from person to person through close physical contact (sexual and non-sexual contact) with someone who has symptoms of mpox. Skin and mucous membrane lesions, body fluids, and scabs are particularly infectious. A person can also become infected by touching or handling clothing, bedding, towels, or objects such as eating utensils/dishes that have been contaminated by contact with a person with symptoms. Household members, family caretakers, and sexual partners of a confirmed case of mpox are at higher risk for infection as are health care workers who treat a case without adequate personal protection.

The incubation period (time between infection and onset of symptoms) ranges from a few days up to 3 weeks. Mpox causes a rash / skin eruption that can be painful associated with swollen lymph nodes and fever. Fever may start already before the rash phase. Other symptoms include muscle aches, back pain, and fatigue. The rash may be localized or generalized, with few or hundreds of skin lesions. It mainly affects the face, the trunk and the palms of hand and soles of the feet. It can also be present in genital areas and on mucous membranes such as in the mouth and throat. Symptoms usually last 2 to 4 weeks and the person remains contagious until all lesions have healed (once the cabs have fallen off).

Complications include secondary bacterial infections, infections of the lung and brain and involvement of other organs, still birth and others. Children, pregnant women, and people with weak immune systems are at higher risk to develop a severe form of mpox.

The majority of person with mpox recovers spontaneously and do not need specific antiviral treatment. Care management consists of relieving pain and other symptoms and preventing complications (e.g., superinfection). Several antiviral treatments are studied in various countries and may be used in trials or in clinical situations according to the recommendations of national medical societies.

In case of symptoms: 

• Seek medical attention immediately
• If you are diagnosed with mpox
  • Please stay at home (isolate yourself) until your mpox rash has healed and a new layer of skin has formed. Staying away from other people and not sharing things you have touched with others will help prevent the spread of mpox. People with mpox should regularly clean and disinfect the spaces they use to limit household contamination.
  • Wash your hands often with soap and water or an alcohol-based hand sanitiser containing at least 60% alcohol.
  • You should not have sex while symptomatic and while you have lesions or symptoms. Use condoms for 12 weeks after infection. This is a precaution to reduce the risk of spreading the virus to a partner.
  • For more information on what do if you are sick, see CDC LINK.

General precautions:

• Worldwide:
  • avoid close, skin-to-skin contact with people who have or may have mpox or people who have a rash (e.g., pimples, blisters, scabs).
  • Wash your hands often with soap and water or an alcohol-based hand sanitiser containing at least 60% alcohol.
  • Avoid touching potentially contaminated personal items such as cups, bedding/clothing, towels or sharing eating utensils/cups, food or drink with a person who has, or may have mpox.
  • Avoid sex with sick persons; use of condoms for up to 12 weeks if you sexual partner have had mpox.
  • Follow advice of local authorities.

• When travelling to endemic / epidemic areas in Africa, in addition to above mentioned general precautions: 
  • Avoid contact with and animals in areas where mpox regularly occurs.
  • Avoid eating or preparing meat from wild animals (bushmeat) or using products (creams, lotions, powders) derived from wild animals.

Vaccination:

There are several vaccines against mpox (e.g. Jynneos®, manufacture Bavarian Nordic). The Bavarian Nordic vaccine was originally developed to fight against smallpox, but offers a cross-protection against mpox. In Switzerland, the Jynneos® vaccine has been licensed by Swissmedic since 2024. Groups at risk (e.g., men who have sex with men or transgender people with multiple sex partners) are eligible for vaccination since 2022 and this recommendation remains unchanged (see FOPH recommendations). In light of the epidemiological situation in Africa in 2024, the Swiss Expert Committee for Travel Medicine recommends vaccination against mpox for professionals who are / will be in contact with suspect mpox patients or animals in endemic/epidemic regions or who work in a laboratory with the virus (for updates, see news).

The risk to the general population and travelers (tourists) is considered extremely low if the above-mentioned general precautions are followed and vaccination is not recommended.

• Seek medical attention immediately.
• Mpox is not a sexual transmitted disease in the strict sense, physical contact with a person with symptoms of mpox (rash at any stage) is sufficient to transmit the disease. Condoms do not protect you from getting mpox!

• Swiss Federal Office of Public Health (FOPH)                                                            
• World Health Organisation: WHO FAQ
• European Center of Disease Control and Prevention (ECDC)
• US Center of Disease Control and Prevention (CDC)