Crimean – Congo Hemorrhagic Fever Outbreaks in Europe

Crimean-Congo hemorrhagic fever (CCHF) is a vector-borne disease (recall that this means transmission by an insect rather than human-to-human transmission or animal-to-human transmission (zoonotic transmission). However, unlike the several diseases I discussed in the last three posts that are transmitted by mosquitoes, this disease is transmitted by a tick. The virus responsible for this disease is called CCHF virus, a Nairovirus, a member of the Bunyavirus family. The CCHF virus causes severe viral hemorrhagic fever outbreaks with a case fatality rate (CFR – recall that this is determined by dividing the number of people who die with the disease by the number of diagnosed cases of the disease and then expressed as a percentage as opposed to the infection fatality rate or IFR, which is the number of deaths due to the disease divided by the estimated number of people infected when there are cases that may be missed due to mild or asymptomatic cases that may never be diagnosed as cases) of 10–40%.

[Note: We still refer to the disease as vector-borne even when the tick or mosquito feeds on an animal, acquires the virus and then transmits it to a human through a bite (in other words, we would not refer to that as a zoonotic transmission). Similarly, we still refer to the disease as vector-borne when the tick transmits the virus to a human and then the virus is then passed on to a fetus by a pregnant mom or to another human through sexual contact, a blood transmission or an organ or tissue donation. In this case, we would still refer to the main transmission as being vector-borne, but acknowledge that there can be limited subsequent human-to-human transmission.]

CCHF is endemic in Africa, the Balkans, the Middle East and Asian countries south of the 50th parallel north – the geographical limit of the principal tick vector.

Unfortunately, there are a wide range of potential hosts of the virus, including cattle, sheep and goats. And, while the virus does not appear to infect most birds, it does infect ostriches, and ostriches have been reported to be the source of infection for humans even though ostriches generally show no evidence of being ill.

While the primary transmission route is via tick bites, CCHF can also be transmitted by close contact with the blood, secretions, organs or other bodily fluids of infected animals when humans slaughter the animals or those of a human in a household or healthcare setting. The majority of cases have occurred in people involved in the livestock industry, such as agricultural workers, slaughterhouse workers and veterinarians.

A tick may transmit the virus to animal, in which the virus may circulate in the animal’s blood for as long as a week. During that time, another tick may feed on the animal’s blood, which may result in the tick carrying the virus to yet another animal or a human and transmitting the virus as it feeds on the animal or human.

Following infection by a tick bite, the incubation period is usually one to three days, with a maximum of nine days. The incubation period following contact with infected blood or tissues is usually five to six days, with a documented maximum of 13 days.

The onset of symptoms is often sudden, with fever, muscle aches, dizziness, neck pain and stiffness, backache, headache, sore eyes and sensitivity to light. Patients can develop a fast heart rate, swollen lymph nodes and a rash that first may be dominated by small, bright, red dots that may then evolve to areas of bruising. In some cases, patients develop swelling and tenderness in the right upper part of their abdomen due to swelling of the liver.

Severely ill patients may experience rapid kidney deterioration, sudden liver failure or respiratory failure after the fifth day of illness.

Patients who recover from this infection generally show improvement by day 9 or 10 of the illness, whereas those who die from the disease most often die during the second week of illness.

The World Health Organization has identified its top 9 list of “priority diseases,” which in the assessment of the WHO present the greatest public health risks. CCHF is on this list. [That list contains Crimean-Congo hemorrhagic fever, Ebola virus disease and Marburg virus disease, Lassa fever, Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS), Nipah and henipaviral diseases, Rift Valley fever, and Zika.]

A virologist at the well-respected Karolinska Institute in Sweden, said that the ticks carrying the CCHF virus were “moving up through Europe due to climate change, with longer and drier summers.” In fact, Spain reported a case of CCHF last year. Iraq has been experiencing a prolonged outbreak of CCHF since last year. Already this year, 100 cases and 13 deaths have been reported. There have also been outbreaks in Namibia and Pakistan. Just this month, Turkey is reporting at least two cases.

Again, the point of this blog piece is:

1. There are many outbreaks occurring other than just the SARS-CoV-2 pandemic.
2. Many of these outbreaks are occurring in countries where these diseases have not been endemic, nor seen other than in international travelers who traveled to the south of the 50^th parallel north.
3. We need to commit to more research of these diseases, the development of therapies and the development of safe and effective vaccines.