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This update is being sent to members of the Wisconsin Travel Health Network.
Global Health Update
Global Measles
In early October, the Department of Health Services (DHS) received a report of a confirmed case of measles in a resident of southeast Wisconsin. In the United States, most measles cases occur in unvaccinated travelers who get infected while traveling internationally. Measles remains a common disease in many parts of the world, including Europe, the Middle East, Asia, and Africa. The Centers for Disease Control and Prevention (CDC) has had a level 1 travel notice in effect since June 2023 due to many international destinations reporting increased numbers of cases of measles. There are currently 39 countries that have reported large measles outbreaks due to low vaccination rates or, in some areas, challenges maintaining a vaccine cold chain. All international travelers without evidence of measles immunity, including infants 6–11 months of age and preschool-aged children, should be fully vaccinated against measles with the measles-mumps-rubella (MMR) vaccine according to CDC’s measles recommendations for international travel.
Measles is one of the most contagious of infectious diseases and can be transmitted via direct contact with infectious droplets and through airborne transmission. Travelers with suspected measles should notify the health care facility before visiting so staff can implement precautions to prevent spread within the facility.
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Cold Weather Travel
When temperatures drop, travel for outdoor adventures can result in cold weather injuries without proper precautions. The most common cold weather-related injuries include hypothermia and frostbite.
Hypothermia
Hypothermia occurs when body temperature drops below 95°F. It usually occurs at very cold temperatures but can also happen at milder temperatures (50°F) if a person becomes chilled from rain, sweat, or cold water. More information on symptoms and treatment of hypothermia can be found in the CDC Yellow Book 2024.
Frostbite
Frostbite occurs when skin is exposed to freezing temperatures. It most commonly affects the extremities such as one’s nose, ears, cheeks, chin, finger, or toes. If severe, it can cause damage to deep layers of tissue under the skin. More information on symptoms and treatment of frostbite can be found in the CDC Yellow Book 2024.
Preventing Cold Related Injuries
Most cold-related injuries result from accidents, unexpected severe weather, or poor planning. It is important to remind travelers planning cold weather activities to take steps to prevent cold- related injuries.
- Wear several layers of loose clothing– inner layers should be light with a wind-resistant jacket for an outer layer.
- Make sure clothing and equipment is appropriate– consider the destination climate, all possible weather scenarios, and all planned activities.
- Stay dry– sweat and wet clothing can chill the body and increase heat loss. Travelers should remove extra layers when actively moving to prevent sweating.
- Prepare a cold weather emergency kit if traveling by vehicle– kits should include things like extra warm weather gear, food and water, a flashlight, and a first-aid kit.
Traveler Health Webpage Update
The Wisconsin Department of Health Services’ Traveler Health Webpage is available as a resource for those traveling or providing care to individuals who are traveling. Travel health care providers can now view previous monthly Travel Health Network Updates on our website under “Resources for health care providers.” Future editions of the Update will be housed on the webpage as well.
Disease Spotlight: African Tick Bite Fever
African tick bite fever (ATBF) is the most commonly diagnosed tickborne disease among returning international travelers. ATBF is transmitted by Amblyomma hebraeum and A. variegatum ticks infected with the bacterium Rickettsia africae. Travel-associated cases of ATBF often occur in clusters with exposure during activities such as safari tours, game hunting, and bush hiking.
Who is at risk?
Travelers to sub-Saharan Africa, parts of the Caribbean, and Oceania (Australia, New Zealand, Melanesia, Micronesia, and Polynesia) are at risk for ATBF. Travelers are at higher risk if their travel plans include outdoor activities such as camping, hiking, and game hunting in wooded, brushy, or grassy areas.
Ticks that are infected with bacteria that cause ATBF fever are usually most active from November through April.
What are the symptoms?
The incubation period for ATBF is most commonly 5–7 days but may be as long as 10 days. ATBF is typically a mild-to-moderate disease, with no known deaths attributable to infection with R. africae. ATBF is almost always associated with an inoculation eschar at the site of tick attachment. Multiple eschars are described in approximately 20–50% of patients with ATBF. Several days after eschar(s) appear, the following can develop:
- Fever
- Headache
- Myalgia
- Regional lymphadenopathy
- Rash (generalized with maculopapular or vesicular eruptions)
How is it spread?
ATBF is transmitted to humans when they are bitten by Amblyomma hebraeum and A. variegatum ticks infected with the bacterium Rickettsia africae.
How is it diagnosed?
ATBF can be presumptively diagnosed in patients with compatible symptoms returning from ATBF-endemic countries. In addition to the symptoms listed above, ATBF cases may have mildly elevated hepatic transaminases, mild leukopenia, or mild thrombocytopenia.
Confirmation of the diagnosis is based on laboratory testing. Contact DHS Vectorborne Disease staff at DHSDPHBCD@dhs.wisconsin.gov or by phone at 608-267-9003 for diagnostic testing guidance and for assistance with specimen submission to CDC.
- ATBF can be confirmed using IHC or detection of Rickettsia africae DNA by PCR at CDC from an eschar swab, skin biopsy, or whole blood.
- A skin biopsy or eschar swab can be collected from patients presenting with an eschar or rash, and have improved sensitivity compared to whole blood.
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R. africae does not circulate in large numbers in blood during the early stage of disease, so whole blood can be a less sensitive specimen.
- ATBF can be confirmed by comparing acute and convalescent samples for evidence of seroconversion in IgG antibodies (demonstration of a four-fold rise in IgG-specific antibody titer). Acute serum should be collected within the first 2 weeks of illness onset, and the convalescent serum should be collected 2–10 weeks after the acute sample.
- Commercially available serologic assays are unable to distinguish between different species of spotted fever group Rickettsia.
Is there treatment for ATBF?
ATBF is treated with doxycycline. Clinical suspicion is sufficient to begin treatment. Delay in treatment may result in more severe illness. These regimens may need to be adjusted depending on a person’s age, medical history, underlying health conditions, pregnancy status, or allergies. Consult an infectious disease specialist in cases of pregnancy or life-threatening allergy to doxycycline.
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Age Category
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Drug
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Dosage
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Maximum
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Duration (Days)
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Adults
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Doxycycline
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100 mg twice per day, orally or IV
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100 mg/dose
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Patients should be treated for at least 3 days after the fever subsides and until there is evidence of clinical improvement. Minimum course of treatment is 5-7 days.
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Children weighing <100 lbs. (45.4 kg)
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Doxycycline
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2.2 mg/kg per dose twice per day, orally or IV
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100 mg/dose
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NOTE: Use doxycycline as the first-line treatment for suspected ATBF in patients of all ages. The use of doxycycline to treat suspected ATBF in children is recommended by both the CDC and the American Academy of Pediatrics Committee on Infectious Diseases. Use of antibiotics other than doxycycline increases the risk of patient death. At the recommended dose and duration needed to treat ATBF, no evidence has been shown to cause staining of permanent teeth, even when multiple courses are given before the age of 8.
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