(CNN) -- Ten new cases of the MERS coronavirus in Saudi Arabia have brought the global total to 104, including 49 deaths.
According to a release sent by the World Health Organization (WHO), the cases include two men from Riyadh who died.
One was 54 and the other 51, the agency said Wednesday.
Middle East respiratory symptom coronavirus, or MERS-CoV, acts like a cold virus and attacks the respiratory system, the U.S.-based Centers for Disease Control and Prevention has said. But symptoms, which include fever and a cough, are severe and can lead to pneumonia and kidney failure.
Precise data are not available on the total number of people who have been infected because it is difficult to tell how many get a mild form of the infection, or remain asymptomatic while infected.
Although many of the cases have occurred on the Arabian Peninsula, people have died of the infection elsewhere, including in four European countries and Tunisia.
In their statement, the WHO advises health care providers in the region to "remain vigilant" and "carefully review any unusual pattern" for those patients who present with Severe Acute Respiratory Infections (SARI).
Coronaviruses cause illnesses ranging from the common cold to SARS, or Severe Acute Respiratory Syndrome, as well as a variety of animal diseases.
Health officials do not yet know much about how the newly discovered virus spreads, which makes it hard for scientists to prevent infections, but the WHO is warning that all recent travelers returning from the Middle East who develop SARI should be tested for MERS-CoV. They refrained from advising special screening points of entry as a result of these latest cases, or travel and trade restrictions.
In the meantime, the WHO is calling for the world to pull together its resources to study and tackle the virus.