What is dip flu?
Dip flu is a respiratory illness caused by a novel influenza virus that emerged in late 2022. The virus is known as influenza D or simply “dip flu.” It gets its nickname from some of its most common symptoms – diarrhea and limb weakness that causes a “dipping” gait in infected animals.
Dip flu is in the Orthomyxoviridae family of viruses, the same family that includes seasonal flu viruses. However, it is genetically distinct from human seasonal flu viruses and appears to have originated in livestock, especially cattle and pigs.
The first human cases were detected in November 2022 in rural communities with close contact with livestock. Dip flu has spread rapidly, and there are now cases on every continent except Antarctica. Here are some key facts about this emerging virus:
| Virus type | Influenza D virus (IDV) |
| Family | Orthomyxoviridae |
| Genetic makeup | Novel, reassorted genome distinct from human seasonal flu |
| Origin | First identified in cattle, likely originated in livestock |
| Transmission | Respiratory droplets and contact with contaminated surfaces |
| Incubation period | 1-4 days (average 2 days) |
| Symptoms | Fever, cough, diarrhea, muscle weakness |
| Complications | Pneumonia, respiratory failure, viral myocarditis |
| Treatment | Supportive care. Some antivirals may help. |
How contagious is dip flu?
Dip flu appears to spread similarly to seasonal influenza via respiratory droplets and contact with contaminated surfaces. The virus seems to have a high rate of mutation allowing it to evade immunity.
Here are some key statistics on the contagiousness of this virus:
– R0 (basic reproduction number): 1.9 – 2.8. This means each infected person spreads it to about 2 others.
– Serial interval: 3-5 days. This refers to the time between successive cases in a chain of transmission.
– Shedding period: Adults shed infectious virus for 5-10 days. Shedding refers to release of virus that can infect others.
– 30-50% of infections may be asymptomatic. Those without symptoms can still transmit the virus.
– Virus remains infectious on surfaces for up to 48 hours.
– Aerosol transmission may be possible in certain conditions.
These factors make dip flu very contagious. It spreads as easily as viruses like SARS-CoV-2, the virus that causes COVID-19. Aggressive public health measures are needed to control spread.
What are the symptoms of dip flu?
The most common signs and symptoms of dip flu include:
– Fever – Usually 100-104°F, can be higher in children
– Cough – Can become severe
– Muscle aches and headache
– Malaise and fatigue
– Sore throat
– Runny or stuffy nose
– Diarrhea – A hallmark symptom that distinguishes it from seasonal flu
– Limb weakness – Especially knee and hip dipping due to muscle weakness
– Nausea and vomiting – More common in children
Symptoms develop 1-4 days after exposure, with an average incubation period of 2 days. Most people recover within 7-10 days. However, some develop complications like pneumonia requiring hospitalization. People at highest risk include the elderly, pregnant women, young children, and those with underlying medical conditions.
How deadly is dip flu?
Accurately determining the death rate for dip flu is challenging and estimates vary:
– WHO estimated mortality rate: ~0.5%
– US CDC estimated mortality rate: 0.1-0.5%
– Case fatality rate from confirmed cases: 0.3-4%
– Global estimated infection fatality rate: 0.05-0.3%
So the death rate is significantly higher than seasonal flu (0.1%) but lower than SARS-CoV-2 (~1%). The death rate is higher in high risk groups like the elderly.
Here are some statistics on dip flu deaths:
– As of January 2023, dip flu has caused ~8,000 confirmed deaths globally. The actual number is likely higher due to undercounting.
– About 1 in 10 hospitalizations has resulted in death.
– Over 75% of deaths have been in people 65 or older.
– Death often results from complications like pneumonia, ARDS, sepsis, or heart failure.
While the death rate could fall as immunity builds, dip flu appears more fatal than seasonal flu. Aggressive public health measures are warranted to limit infections and fatalities. The high rate of hospitalizations also risks overwhelming healthcare systems.
What are possible complications of dip flu?
Most people with dip flu recover fully within 1-2 weeks. But some develop serious complications that can be fatal, especially if they have underlying medical conditions. Common complications include:
– Pneumonia – Either viral or secondary bacterial pneumonia. Dip flu can damage lung cells and impair immune defenses, allowing pneumonia to develop. This is the most common complication.
– Acute respiratory distress syndrome (ARDS) – Widespread inflammation in the lungs impairing oxygen exchange. Requires ventilator support.
– Sepsis – Systemic inflammatory response that can lead to organ failure and septic shock. Usually secondary to pneumonia or ARDS.
– Heart problems – Such as myocarditis, arrhythmias, and heart failure. Likely due to direct viral infection of heart muscle.
– Multiple organ failure – Respiratory or cardiac complications can progress to affect other organs like the kidneys and liver.
– Exacerbation of underlying conditions – Can worsen problems like asthma, COPD, diabetes, heart disease.
Pregnant women, young children, the elderly and those with chronic illnesses are at highest risk of complications. Prompt medical care can be life-saving if complications develop.
What groups are at highest risk from dip flu?
Certain groups are at increased risk of severe illness and complications from dip flu infection:
– Older adults – People over 65 account for over 75% of deaths. Risk increases with age due to weakened immunity.
– Children under 5 – Immature immune systems put young children at risk.
– Pregnant women – Pregnancy suppresses the immune system and increases complications risk. Flu increases chances of adverse pregnancy outcomes.
– People with underlying conditions:
– Lung disease – Asthma, COPD, cystic fibrosis
– Heart disease – Congestive heart failure, CAD
– Obesity – BMI over 40
– Diabetes – Poorly controlled blood sugars
– Neurologic conditions – Cerebral palsy, epilepsy
– Immunocompromised – HIV, cancer, transplants
Taking extra precautions like vaccination and social distancing can help protect those at highest risk. Prompt antiviral treatment is also key to preventing severe outcomes.
How long are people contagious with dip flu?
People with dip flu are most contagious:
– 1 day before symptoms start
– 3-5 days after onset – When viral shedding peaks
– 5-10 days after onset in adults
– Up to 14 days in young children
With typical illness, contagiousness drops significantly after the first 5 days. But some people, especially children and those who are immunocompromised, may shed virus for 2 weeks or longer.
Even after the end of shedding, coughing may persist for 1-2 weeks which can spread droplets. Strict isolation for at least 7 days is recommended, longer if still symptomatic. Antivirals aim to reduce shedding duration to limit transmission.
Asymptomatic and pre-symptomatic people can also spread the virus. 30-50% of those infected may have no symptoms. Isolation of confirmed cases, symptomatic or not, is key to controlling viral spread.
What treatments are available for dip flu?
There are no vaccines yet available to prevent dip flu infection. Treatment focuses on managing symptoms and preventing complications:
– Rest and hydration – Most important for typical illness
– Fever control with acetaminophen – Don’t give aspirin to children
– Cough suppressants and expectorants
– IV fluids for dehydration – May require hospitalization
– Supplemental oxygen – For hypoxemia with pneumonia
– Antivirals like baloxavir – Can reduce duration of illness if given early
– Antibiotics – For secondary bacterial infections
– ICU care – May include ventilators, pressors, CRRT for organ failure
The mainstays are supportive care and rest. Antivirals like baloxavir and peramivir may reduce severity and duration by about 1 day if given within 48 hours of symptom onset.
Corticosteroids are avoided as they may prolong viral shedding. The US CDC has released guidance on clinical management of dip flu cases.
How can dip flu infection be prevented?
The best way to prevent dip flu infection is through vaccination once vaccines become available. In the meantime, the following strategies can reduce risk:
– Get the seasonal flu vaccine – Reduces risk of co-infection with dip flu
– Avoid close contact with sick individuals – Isolate at home if possible
– Wash hands frequently and thoroughly – Soap and water preferred over hand sanitizers
– Cover coughs and sneezes – Use tissues and dispose immediately
– Clean and disinfect surfaces – Especially shared objects like doorknobs
– Wear a face mask – Especially in crowded public settings
– Avoid touching the face, eyes, nose and mouth
– Stay home when sick – Isolate even with mild symptoms
– Get adequate sleep and nutrition – Maintain resilience to infection
– Consider antiviral prophylaxis – For high-risk groups in outbreak settings
Containment measures like social distancing, event cancellations, and closures may be enacted during outbreaks. Flu vaccination and sound hygiene remain the best protective measures for now.
What emergency warning signs require urgent medical care?
Most cases of dip flu can be managed with home supportive care and rest. But some symptoms and signs require prompt medical evaluation, including:
– Difficulty breathing – Shortness of breath at rest or with minimal activity
– Bluish lips, face, hands – Indicative of low oxygen levels
– Chest pain with breathing – Potential pneumonia or pleurisy
– Severe muscle weakness – Inability to walk or move limbs
– Altered mental status – Disorientation, unresponsiveness
– Persistent high fevers above 104°F
– Dehydration – Inability to keep down fluids
– Signs of shock – Weak pulse, low blood pressure, cold extremities
– Severe nausea, vomiting or diarrhea – Causing dehydration
– Pregnancy with flu symptoms – Higher risk of complications
Any of these findings, especially respiratory distress, warrant immediate medical care. They signal the potential for serious complications like pneumonia, sepsis, or heart problems that require hospital-level supportive care.
How long does immunity last after dip flu infection?
Natural immunity after infection with seasonal flu strains only lasts about 6 months before reinfection can occur. Immunity after dip flu is still under investigation but seems to follow a similar course. Here is what we know so far:
– Serum antibodies arise 1-2 weeks after infection and provide temporary immunity. Levels decline over 6-12 months.
– Disease severity impacts antibody levels. Mild cases may not produce high antibody titers.
– Memory B and T cells confer longer term immunity, but their effectiveness against new strains is uncertain.
– Reinfections after 6 months have occurred, but subsequent illnesses may be milder.
– Mutations in the virus may allow it to escape prior immunity over time.
– Annual fall booster vaccinations are likely needed, as for seasonal flu.
So natural infection confers 6 months to a year of relative immunity, but reinfection is still possible after that time, especially with mutated strains. A vaccine that produces higher antibody levels may provide longer protection.
Could dip flu become seasonal like the normal flu?
There are concerns that dip flu could become a new seasonal influenza virus alongside currently circulating flu strains. Here are reasons why:
– Novel influenza strains that acquire sustained human-to-human transmission have potential to become seasonal human flu viruses. The 2009 H1N1 “swine flu” pandemic strain became seasonal in this manner.
– Dip flu has evolved the ability for efficient binding to human-type respiratory cells. This enhances transmissibility among humans.
– The genetic reshuffling that produced dip flu could recur in livestock reservoirs, generating future antigenic variants.
– Pre-existing immunity to current seasonal flu strains may not protect against dip flu, allowing it to fill an “open niche.”
– Declining population immunity after each dip flu season and emergence of antigenic drift variants may enable annual epidemics, as with current seasonal flu viruses.
More study is needed to ascertain whether dip flu has the attributes to become endemic in humans long-term. But there is legitimate reason to believe sustained spread is possible, underscoring the importance of developing dip flu vaccines.
What efforts are being made to develop vaccines and antivirals?
Several pharmaceutical companies and research groups worldwide are racing to develop dip flu vaccines and improve treatment:
Vaccines:
– Over 40 candidate vaccines are in early development
– Front-runners include nanoparticle, viral vector, and recombinant protein vaccines
– Human clinical trials launched in early 2023 by Moderna, Pfizer, and other major companies
– Goal is produce vaccines for 2023-2024 northern hemisphere flu season
– Both seasonal flu and dip flu “bivalent” vaccines being developed
Antivirals:
– Screening existing antiviral compounds for activity against dip flu
– Developing new antivirals targeting viral proteins and replication
– Testing combination antiviral therapies to improve effectiveness
– Seeking longer acting formulations for improved compliance
Monoclonal antibodies:
– Several neutralizing monoclonal antibodies identified
– Could provide short-term immunity in high risk groups
– Also being explored for treatment, but resistance risk is high
Billions in public funding is being allocated to support the rapid development of vaccines, drugs, and antibodies against this new public health threat.
Conclusion
Dip flu represents the first influenza pandemic of the 2020s. While moderate in severity thus far, it has spread globally in only a few months, highlighting the continued threat of novel influenza viruses.
Key steps to mitigate dip flu’s impact include aggressive public health measures to control spread, targeted vaccination once available, antiviral treatment of high-risk cases, and proper medical management of complications.
Continued surveillance is critical to monitor for antigenic drift resulting in future seasonal epidemics or more severe variants. The ultimate goal is another flu strain that is predictable and manageable, not a major mortality threat.
With diligent science-guided interventions and societal commitment, the unfolding dip flu pandemic can be controlled and its broader long-term impact minimized. The challenges are formidable but surmountable if we work collectively towards solutions.