News Coronavirus What is a virus 'reproduction rate'?

What is a virus ‘reproduction rate’?

Global alarm was sounded on Monday over a potential second wave of coronavirus infections after Germany reported that the reproduction rate of the pathogen had risen above 1, indicating the disease was again spreading just days after the first tentative steps there to reopen the economy.

The following explains what a virus reproduction rate is and why it is important in understanding the implications of ending economic lockdowns aimed at containing the spread.


The reproduction rate, or RO (pronounced R-naught), of a virus is a measure of its transmission, or the number of new infections generated by each case. An RO rate of 1, for example, means on average each infected person will infect one other person they come in contact with.


A reproduction rate of less than 1 means that an outbreak is subsiding, since each infected person is transmitting the virus to fewer than one other person.

An RO rate above 1 means the virus is spreading exponentially, with each contagious person infecting more than one other person. An RO of more than 1 is also an indication that hospitals and healthcare systems are vulnerable to becoming overwhelmed.

During the fast-spreading initial outbreak of the coronavirus in Wuhan, China, the reproduction rate was estimated at around 2.5, according to a World Health Organization analysis.


Calculating the reproduction rate can be difficult, especially for a large country like the United States, with widely divergent demographic regions. “In rural Montana, the R-naught might be less than one. In urban areas … it might be R1, or maybe a little bit more than that,” said Dr. William Schaffner, professor of preventive medicine and infectious diseases at Vanderbilt University Medical Center in Nashville.

A lack of capacity for widespread testing would also make it difficult to accurately assess the transmission rate.


Population density is a major factor. The virus spreads much more efficiently in densely populated areas. Mitigation efforts, such as social distancing, school and business closures, and wearing of face masks all help drive the RO number down.

The characteristics of the virus itself is another major influence on its RO rate. This new coronavirus has demonstrated an ability to spread more easily than other viruses, such as influenza. It has a median incubation period of about 5 days, compared with 2 days for flu, and people with no symptoms of infection can spread the virus to others. In addition, there has been evidence of transmission from close contact with an infected person even without virus particles spreading through coughing or sneezing.

The level of immunity in a population, either from previous infection with a virus or from vaccination rates will also influence the RO. In this case, there is no approved vaccine and no one had immunity when the virus first emerged.


The short answer is “yes.” That could be an indication of a new surge of infections.

News that the reproduction rate had climbed back to 1.1 in Germany, which had been held up as a coronavirus mitigation success story, cast a shadow over the reopening of businesses on Monday from Paris hair salons to Shanghai Disneyland, and the easing of restrictions across the United States.

While the political decision to start reopening state and local economies in the United States has already been made, caution is needed, Schaffner stressed.

“If you open up too fast, all of a sudden the medical problems increase,” he said. “It is a delicate balancing act. We shouldn’t move too quickly.”


Top Stories

France recalls ambassador to Ankara over Erdogan comments

  France condemned Turkish President Recep Tayyip Erdoğan’s remarks questioning the mental health of President Macron and recalled its ambassador to Ankara for consultations. The French...

130 cases today, most from private initiative-28 patients in hospital

  One hundred and thirty new Covid-19 cases were announced today, out of 4 thousand 285 tests, taking the total number of confirmed patients to...

Greece approaches four-digit covid cases, 935 today

  The second coronavirus wave is climaxing in Greece as it recorded 935 cases today, the highest number since the second wave begun gathering pace...

Erdogan says Macron needs ‘mental treatment’ over attitude to Muslims

  Turkish President Tayyip Erdogan launched yet another scathing tirade of insults on his French counterpart Emmanuel Macron, saying he needed mental treatment over his...

We are independent, Michaelides tells AG over golden passports

  We are not under anyone's custodianship, the Auditor General Odysseas Michaelides told Attorney General Yiorgos Savvides, who earlier called on his office to stay...


Squash soup

Ingredients: 1 kg pumpkin, cut into small cubes, approximately 5 cups 2 medium (400g) sweet potatoes, cut into cubes, approximately 2 ½ cups 1 chopped leek, only...


No visit to Cyprus is complete without enjoying the traditional meal of many small dishes known as ‘meze’. This large feast, which has been a...

Prawns with fried cheese, barley shaped pasta

Put the barley shaped pasta into a small pan with salted water, bring to a boil and when tender, drain. Peal the prawns leaving...

Salmon and shrimp sheftalies

Mix all ingredients for tabbouli in a bowl and keep to one side so flavours can combine. Prepare the sheftalies: wash and soak the casing...