Middle East respiratory syndrome (MERS)

MERS is a rare but severe viral infection of the airways. The virus lives in dromedary camels and reaches people through close contact with the animals, their raw milk or undercooked meat. It passes poorly from person to person, yet it flares readily wherever seriously ill patients are nursed at close quarters. For a traveller who never went near a camel the risk is close to zero. But if a fever and cough appear within a fortnight of a trip to the Arabian peninsula, mention that trip in the first minute of the consultation: it decides which test you are sent for.

How the virus reaches people

The main source is the dromedary camel. In the animal itself the infection looks like a mild head cold, but it sheds virus, and a person catches it through close contact: stroking, feeding, riding, mucking out a pen, breathing dust in a camel shed, helping at a birth.

The second route is food. Raw camel milk and drinks made from it, undercooked meat, and camel urine, which in some places is drunk as a folk remedy, all carry live virus. Pasteurisation and ordinary cooking destroy it.

Between people the virus spreads less readily than flu or COVID-19: it takes prolonged, close contact. That is why the overwhelming majority of such cases arise in two settings — a family nursing a patient at home, and a hospital that admits someone without knowing the diagnosis and keeps them for days on an open ward. The person in the next aeroplane seat or a passer-by in the street does not catch it this way.

Where the risk is real

Almost all cases since 2012 have come from the Arabian peninsula, above all Saudi Arabia; patients have also been reported in the United Arab Emirates, Qatar, Oman, Jordan and Kuwait. The virus has been found in camels in the Horn of Africa and North Africa, but human cases there are few.

Outside the region, cases are imported: someone flies in already infected. That is how the large South Korean outbreak began, when one returning patient went round several clinics and dozens of people were infected, all of them inside healthcare buildings.

It is not countries that are dangerous but particular places and activities: camel farms, livestock markets, abattoirs, races and festivals with camel rides, tasting raw milk, and also accompanying a patient in a hospital in the region. An ordinary trip of city, hotel and beach carries almost no risk.

How the illness begins

Between infection and the first complaints there are two to fourteen days, most often five or six. It starts with a high temperature, chills, aching muscles and headache; then come a cough and increasing breathlessness. In many people pneumonia develops quickly.

About a third of patients also have digestive symptoms: diarrhoea, nausea, vomiting and abdominal pain. Sometimes these dominate the first days and the person assumes they have eaten something bad.

Some of those infected have a mild illness or none at all, and are picked up when contacts are screened. The other side of the coin is that in severe cases the condition often deteriorates sharply in the second week, just when the worst seemed to be over. That is why breathing is watched even when the patient seems reasonably well.

Who becomes seriously ill

Severe illness is commoner in older people and in those with long-term conditions. Chief among them are diabetes, chronic kidney disease — especially on dialysis — long-term lung and heart disease, and marked obesity.

A separate group are people whose immunity is weakened: after an organ transplant, during chemotherapy, or on long-term medication that suppresses the immune system. In them the illness is both more severe and recognised later, because the temperature may stay low.

The proportion of deaths among officially recorded patients is high, around a third. That figure needs reading correctly: the statistics mainly capture people admitted to hospital, that is the severe end, while mild and symptomless infections go uncounted, so the true death rate is lower. Children and healthy young adults mostly have a mild illness.

When to call an ambulance and when to see a doctor

Call an ambulance (in Spain, Italy, Portugal, Poland and Ukraine the single number is 112) if the patient has:

• severe breathlessness — not enough air to finish a sentence, rapid breathing, with the spaces between the ribs and the hollow above the breastbone drawing in on each breath;
• lips, face or fingertips turning blue or grey; on darker skin look at the lips, gums, palms and soles;
• confusion: not knowing where they are, not answering simple questions, or being impossible to rouse;
• crushing or sudden severe chest pain;
• sudden weakness, fainting, cold clammy skin, or almost no urine passed in half a day.

Nobody in that state should drive themselves to hospital. While you wait for the ambulance, open a window, sit the person upright and do not leave them alone.

Contact a doctor the same day, ideally by telephone first, if within fourteen days of returning from the Arabian peninsula you develop a fever, cough or breathlessness; if you have been in contact with camels or drunk raw camel milk; or if someone around you has confirmed MERS. Say in advance that you have travelled: you will be seen away from the general waiting area and given a mask. There is no need to ring 112 for this — an ambulance service does not decide who is tested and when.

How the diagnosis is confirmed

The diagnosis rests on PCR, a search for the virus's genetic material in the airways. There is an important catch: the usual rapid tests for flu and COVID-19 do not detect this virus. A specific MERS-CoV test is needed, and the laboratory has to know it should look for it. Hence the insistence on hearing about the trip.

The sample is best taken from the lower airways — sputum, tracheal aspirate, or washings obtained at bronchoscopy. A nose and throat swab is taken too, but it is less sensitive: one negative swab in the face of a clear suspicion rules nothing out, so the test is repeated and supplemented with a deeper sample.

Alongside this a chest X-ray or CT scan is done, and pneumonia is usually visible, often in both lungs. A normal film in the first days does not exclude the illness. A full blood count often shows low lymphocytes and platelets; biochemistry covers kidney and liver function, and oxygen saturation is measured with a pulse oximeter. An antibody blood test is of little use in the acute phase: it shows past infection and is used to investigate outbreaks, not to make the diagnosis.

What is done in hospital

There is no medicine of proven effect against this particular virus, and no vaccine for people. Treatment is supportive, and it can carry a severely ill patient through: oxygen by mask and, as respiratory failure advances, non-invasive breathing support or mechanical ventilation, and in the most extreme cases ECMO. Intravenous fluids, medicines to bring down fever and relieve pain are added, and kidney function is monitored.

Antibiotics have no effect on a virus. They are given only when a bacterial infection has been added on top, and that is a decision for the doctor based on tests and imaging, not for the patient.

Such patients are nursed in a single isolation room, with staff in respirators, eye protection and gowns. Close contacts are monitored for fourteen days and tested at the first symptom. Mild cases are sometimes managed at home, but again with isolation and follow-up.

How to lower the risk while travelling

The main rule is simple: keep away from camels and from everything connected with them. Do not stroke them, do not ride them, do not go into farms, livestock markets or pens, and do not push closer to watch a race. If work or circumstances do bring you into contact with the animals, wash your hands with soap straight afterwards and keep them away from your face.

Do not taste raw camel milk or products made from it, do not eat raw or undercooked meat and offal, and do not drink camel urine in any form or on anyone's advice. Wash and peel fruit and vegetables from street markets yourself. Stay away from animals that look ill.

Anyone with diabetes, kidney disease, long-term lung disease or weakened immunity should avoid farm visits and hospital visits in the region altogether: this is the group at highest risk of severe illness. Ordinary hand hygiene, avoiding food from doubtful stalls and washing your hands after public transport matter just as much on such a trip.

Online consultation

An online conversation is most useful exactly where the question is whether any testing is needed at all. You describe where you have been, what you did, when the fever started and how your breathing feels, and you get a clear answer: watch calmly, go and have the specific MERS test, or call an ambulance right now. The doctor will also explain how to attend an appointment without infecting anyone: ring ahead, wear a mask, do not sit in the general waiting room.

The same format helps after the illness — going through the discharge summary, understanding why the cough and fatigue drag on for weeks, deciding whether a follow-up X-ray is needed. The limits are obvious: listening to the lungs, taking a sputum sample and measuring blood oxygen cannot be done through a screen. With worsening breathlessness, blue discolouration or confusion, what is needed is not a call to the doctor but an ambulance.

This material is for information only and does not replace medical advice.