Coronavirus Spread: Here's what WHO experts are tracking
The virus has spread to at least 27 countries and territories, according to a Reuters count based on official reports, infecting more than 330 people outside China. The two deaths outside mainland China were in Hong Kong and the Philippines.
The World Health Organization (WHO) is tracking the epidemic of the new coronavirus in China and how it is spread abroad, as its advance team of international experts travel there to help investigate the outbreak.
The death toll from the epidemic rose to 908, all but two in mainland China, on Sunday as 97 more fatalities were recorded - the largest number in a single day since the virus was detected in the city of Wuhan in December.
WHO chief Tedros Adhanom Ghebreyesus said there had been "concerning instances" of transmission from people who had not been to China.
"The detection of a small number of cases may indicate more widespread transmission in other countries; in short, we may only be seeing the tip of the iceberg," he said in Geneva.
The virus has spread to at least 27 countries and territories, according to a Reuters count based on official reports, infecting more than 330 people. The two deaths outside mainland China were in Hong Kong and the Philippines.
The death toll from the outbreak has now surpassed that of Severe Acute Respiratory Syndrome (SARS), which killed hundreds worldwide in 2002/2003.
Here are some issues that WHO epidemiologists are probing to deepen understanding of the virus, believed to have jumped the species barrier at a seafood market in Wuhan in December, to help accelerate development of drugs, diagnostics and vaccines.
- Human-to-human spread: WHO says that an infected person transmits the respiratory virus through droplets or close contact, but that it can stay on surfaces for short periods. It has a maximum incubation period of 14 days.
- To what extent people who have mild disease, which according to Chinese data on 18,000 cases is some 82%, shed the virus and potentially expose others. Some 15% of cases are severe and 3% critical, according to its data shared with WHO.
- So-called 'clusters' of cases where there has been secondary or tertiary onward spread of the virus among people in countries including China, Germany and France. Tracing contacts exposed to the virus is key to stopping transmission chains.
"The overall number of people associated with those clusters has been very, very limited," Dr. Mike Ryan, WHO's top emergencies expert, said on Saturday. "Those clusters also can teach us a lot about the nature of the dynamics of disease transmission."
- Spread of the virus in hospitals and health care facilities, where the WHO advises medical staff to take standard infection prevention and control measures including wearing gloves, masks and gowns.
"From the start when we knew about this new respiratory pathogen, and it was a coronavirus, we thought that there was going to be the possibility of an amplification event, or 'super-spreading' events," said Dr. Maria van Kerkhove, a WHO epidemiologist.
"We have only one instance of an outbreak in a hospital that we are aware of, in Wuhan, involving 15 health workers," she said.
- Why some people die. People who are older or have underlying medical conditions - including cancer, diabetes, and hypertension - are most at risk. The overall death rate among reported cases is some 2%. People above 80 have the highest death rates, WHO says, citing Chinese data. WHO wants more data about the disease that can cause pneumonia and organ failure.
"We have recently released a clinical case report form which we are encouraging hospitals and clinicians to use so that standardised data collection can be captured from patients who are hospitalised," van Kerkhove said.
This will provide a better picture of disease progression and what severe disease looks like, she said.