Measures to delay the spread of coronavirus, Covid19

This is a rapidly evolving situation and advice may change at short notice

Covid19 is the new disease caused by novel coronavirus.

There are many known unknowns about this new disease:

- the proportion of people who will require hospital admission
- the proportion of people who will require mechanical ventilation
- the proportion of people who die from the disease (the Case Fatality Rate, or CFR)
- the number of patients who are infected in Scotland
- how long viral particles survive on surfaces
- whether the virus is droplet spread or has some aerosol spread
- what the long´term effects will be on survivors of serious illness

But some things are known:

- most patients have mild or very mild symptoms
- the disease can cause breathing problems and death
- a proportion of patients require oxygen therapy or mechanical ventilation to survive
- patients over 60 and with chronic illness are at much higher risk
- the disease is very contagious
- populations have no immunity to the disease because it is new
- a vaccine is at least a year away
- detected cases are rising rapidly in the UK and Scotland

Infectivity (R0)

The ease and speed with which viruses spread is called the R0.  This is the number of people that each infected person will infect on average.  The R0 for novel coronavirus before any public health intervention was between 4.7 and 6.6.  That is to say, it is very contagious.  For comparison, this is  similar to smallpox, mumps, and polio but much more infectious than seasonal influenza  (R0 approx 1.3 to 2.0).

A virus with a high R0 can be greatly affected by public health strategies such as the ones seen in China - society changes to greatly reduce human contact.  This has dropped the R0 down to around 2-3.

This is why we don't quarantine influenza cases and make massive societal changes to limit the spread of seasonal influenza.  Influenza has a lower 'natural' R0 and so these techniques are less effective for influenza.

Novel coronavirus appears able to spread before symptoms appear and from people with few or even no symptoms.  This is different from SARS, MARS, and Ebola and means that containment by tracing contacts of positive cases is unlikely to be successful at stopping the virus, only slowing it down.

Case Fatality Rate (CFR)

The case fatality rate measures the number of people who die as a percentage of infected people.  Since many people have mild or very mild symptoms, the true number of people infected by novel coronavirus may never be known.  Also, because it can take many weeks from being infected to the time someone dies, the fatality rate cannot be easily calculated during an epidemic/pandemic.

Attempts have been made to estimate the case fatality rate.  In China the rate for children and young adults was very low at around 1 death per 500 positive cases.  However, the rate rose sharply after the age of 60 and the rate was around 1 death per 7 positive cases in over 80s.  Adult patients with chronic conditions such as diabetes and asthma also had higher rates of death.

Lay people often make the error of thinking that the lethality of Covid19 is similar to that of seasonal influenza.  The lethality of seasonal influenza is very low, but even the highest estimates of 1 death per 1000 cases are around 10x lower than the lower estimates of novel coronavirus (1 in 100 cases).  Also, there is a degree of herd immunity to seasonal influenza as the strain usually only shifts a little each year.  So, only around 10% of people will catch seasonal influenza each year.  There is no immunity to novel coronavirus, and 30 to 80% of people are likely to be infected in the first year.

Community Spread

The number of people who are infected in the community is unknown.  Current policy is only to test people who have been in a country with known community spread or who have been a close contact of a person who has already tested positive.  The problem with this is that large number of cases can go undetected.  For example, in Washington State, it was only realised that community spread had likely been ongoing for several weeks in the state when the first serious cases came to light. 

Contain and delay

Information from Italian doctors at the time of writing is that up to 10% of their positive cases required admission to intensive care units for mechanical ventilation.   The UK is very limited in the number of hospital beds and especially intensive care beds per head of population compared to the great majority of G20 countries.   It is essential that we delay cases as long as possible to minimise the number of deaths from lack of hospital facilities.

That is to say, patients with severe disease who are unable to get oxygen therapy and/or intensive care because of lack of beds will die who otherwise would have survived if the spread of the virus had been delayed. 

Issues specific to Strachur.

Strachur is a remote location with a very high proportion of older patients and patients with chronic illnesses.  Strachur  Medical Practice has only 2 doctors and one nurse and is the only health care provider in the area.

The patients in Strachur are at higher risk than an average community.   If a patient was to attend the surgery and then be suspected of being Covid19 the practice would cease to be able to look after patients, perhaps for a prolonged period.

Practice risk to patients

The people at highest risk of being infected in Strachur are the staff of the medical practice, as they come into contact with more sick people than anyone else.  Health care staff frequently work through illness out of dedication to their patients.  The most likely outcome is that the staff will have mild or very mild symptoms but will be contagious to patients and will contaminate the surgery.

Another common scenario is that multiple patients who are older and/or have chronic illness spending 30 minutes or more in a crowded waiting room will be infected by someone with mild Covid19 illness attending the GP.

To minimise the risk of the practice becoming a focus of infection in the community, Strachur Medical Practice will take a series of steps when the doctors think that community spread is either already ongoing or is imminent.

Steps the practice will take to protect patients

The doctors at Strachur Medical Practice now believe that community spread in Scotland is either already underway or is imminent.

To protect patients we need to minimise patients' exposure to the waiting room and other patients.  We also need to avoid a patient with suspected Covid19 attending the surgery.  The practice will therefore:
- close its doors to walk ins
- provide telephone appointments to all patients
- continue telephone triage for urgent cases
- ask patients to collect their dispensed medications from the dispensary window to avoid entering the building
- patients who require to be examined will be invited to attend the most suitable location at a suitable time.

Steps patients can take to protect themselves

- older patients and patients with chronic illness should avoid contact with other people as much as possible.
- keep a meter away from other people
- do not shake hands
- avoid touching your mouth or nose
- wash your hands for 20 seconds with soap and water regularly
- store deliveries for several hours before handling them to reduce the viral load on 'fomites' (objects that may have viral contamination).